Now on to the boss breakdowns:
Each boss has been rated with an efficiency rating that is loosely based off of a combination of how much time you can expect to be waiting between summons, level conditions leading up to the boss, and the boss fight itself. These ratings are not set in stone and may vary greatly depending on your location and what time you play, but generally the higher the efficiency rating then the higher your chances of beating the boss for co-op rewards. Assume for these ratings that you are playing when traffic is likely to be highest. The ratings are as follows:
0: Never going to be summoned unless it is prearranged with a friend.
1: Summons may happen, but they are very rare. No specific time range, because too little co-op takes place in this area for any to be measured.
2: Summons do happen, but you're going to have to wait. Some people may want help with this boss, but poor co-op conditions of the level or lack of a reliable summon sign location make these boss areas unreliable for successful summons.
3: The level and the boss fight are bearable, but the maximum of most of our patience levels fits here. Expect wait times of up to 20 minutes.
4: Expect wait times of up to 15 minutes, though faster is not unheard of. Take these areas to do your laundry/homework/pick up your room/etc. You'll get some breather time, but don't go too far away.
5: You will get summoned within as little as 1-10 minutes. High traffic and highly assistance-worthy bosses ensure quick summons.
If your level is at least 10 levels higher than the recommended levels, expect the efficiency to be that of a level 2, any higher and expect efficiencies of level 1 only.
Important Note: an important exception to these general guidelines is that many players finish their "builds" at level 120, and continue playing into NG+ and beyond. As a result, characters at or around level 120 are found in all areas of the game, and summoning at that level can be frequent anywhere. The below guidelines are most relevant to players still in NG.
Asylum Demon, Stray Demon:
Summoning Efficiency: N/A
Recommended Level: N/A
Pros: None
Cons: It is impossible to even drop a summon sign in the Northern Undead Asylum, therefore making it impossible to be summoned.
Taurus Demon:
Summoning Efficiency: 4 (0 above level 150)
Recommended Level: 5-10
Pros: As the Undead Burg is usually the first area players try to beat after leaving the Asylum, you are more likely to encounter new players as hosts who definitely need help, which can feel rewarding. Since there is no summoning in the starting Asylum area, this is also often the first time the host has seen summoning signs and summoned someone, so don't expect them to necessarily know anything about the level or even what your role as a summon is. This area also has an increasing number of low level but well outfitted invaders, which can make for a lot of fun and give the host a fast introduction to PvP. The most popular place for both summoning signs and invasions is outside the bonfire near the catwalk with the Hollows throwing firebombs.
Cons: The Undead Burg is a PvP hotspot, so be aware that not all hosts summoning in this area are doing so for boss runs. Summoning for PvE in this area drops pretty quickly beyond soul level 15. Just stay a bit underlevelled until you beat the Taurus Demon yourself, and talk to Solaire afterwards to get your White Sign Soapstone, then return to the Undead Burg and place your sign. Also expect inexperienced hosts to find all sorts of interesting ways to get themselves killed along the way, leading to a higher than usual number of environmental deaths compared to other areas. Many invaders will have pushed fairly far into the game before returning here, so it is also to your benefit to do things such as get an upgraded pyromancy glove and higher strength pyromancies to even the odds.
Bell Gargoyles:
Summoning Efficiency: 5 (2 above level 150)
Recommended Level: 15-25
Pros: Incredibly simple boss, lots of hosts wanting help with them, easiest place to be summoned for early entry to the Warriors of Sunlight.
Cons: Tricky summon sign locations. Since there are no bonfires that are actually nearby, you can't follow the general rule very well. The best locations for this area are at the bottom of the stairs leading into the church just outside the bridge to Blacksmith Andrei's Tower where you fight 3 hollowed soldiers, and at the bottom of the stairs inside the church next to the elevator shortcut back to Firelink Shrine. A third option is on the main stairs leading up to the armored boar, past the bonfire near the Sunlight Altar. If summoned there, be prepared to guide the host down under the alternate route if the portcullis behind the boar is down. Finally, one can also place signs at the doorway leading out under the bridge, to pick up hosts arriving either from the Burg bonfire (if the ladder is down) or who are trying to avoid the bridge wyvern.
Capra Demon:
Summoning Efficiency: 4 (2 above level 150)
Recommended Level: 20-30
Pros: Lots and lots of people want help with this boss, and the short length of the preceding level and relatively quick boss fight can make for frequent summons.
Cons: Odd summon sign location, the current best being on the small bridge right before his area gate, making this one of only 2 bosses you can acceptably put your sign right in front of the arena. The other preferred location is at the very beginning of the area, before the stairs down leading to the undead hounds and large bonfire. Invasions are common, so expect PvP. The fight itself is sometimes difficult to co-op as the Capra Demon and 2 dogs can swarm the host before the summons have time to follow through the fog gate, and a phantom sometimes gets in the way of the host due to the small boss area. If you are using a heavy weapon, try to stagger the Capra Demon as soon as you enter to buy the host time to deal with the dogs or get up the stairs to a safer location.
Gaping Dragon:
Summoning Efficiency: 4 (2 above level 150)
Recommended Level: 25-35
Pros: Easy fight, if long due to its high health. Going against the general rule of summon sign location, it is also fairly common to place signs right at the beginning of the area on or around the landing before the stairs leading down to the Hollows/Butchers, as many players come directly to the Depths in Human form after beating the Capra Demon with the help of summons. A summon who helps defeat both the invading NPC Darkwraith Kirk and the Gaping Dragon can earn upwards of 20,000 souls for what is often just a few minutes of work once summoned. The ability to farm Humanity items, various Titanite shards, and Eyes of Death from the rats, slimes, and basilisks respectively while waiting to be summoned also helps keep this typically optional area popular.
Cons: Depending on how much the host has cleared, the area before can be a breeze, or frustrating. If they haven't already opened the shortcut, expect a cramped and directionless run through the Depths. If you can, try to be a guide if the host doesn't seem to know where to go or gets lost. In particular, learn how to quickly get down into the Basilisk area from any place on the map, as hosts routinely fall into it from the open drains or waterfall. High curse resistance gear such as the Paladin Set or Antiquated Set (particularly the skirt) will enable you to rescue them quickly in such an event. Even if it looks like some of the area may have been cleared, on the way to the Gaping Dragon it is also worth a short detour down past the giant rats near the bottom of the shortcut stairway to ensure that Darkwraith Phantom Kirk invades (as this is the first of his 3 appearances, sometimes the host will not realize they didn't trigger it).
Chaos Witch Quelaag:
Summoning Efficiency: 5 (3 above level 150)
Recommended Level: 25-40
Pros: Simple fight with multiple people, HUGE amounts of souls for the level you fight at. The route from the nearest bonfire at the bottom of Blighttown to Quelaag's lair is one of the shortest and easiest in the game when done properly, and combined with the large amount of souls from the fight makes it possible to collect a great deal of souls and humanity in a short amount of time. This is particularly helpful for those who need both for Chaos Servant and/or pyromancy purposes.
Cons: The area before can get you if you aren't prepared. Bring some Purple Moss Clumps so you don't doom yourself with poison before even being summoned. It is very easy and quick to get to Queelag from the favored summoning area around the bonfire at the bottom of Blighttown, but if you notice the host picking up items along the way you should consider leading them on a full circuit of the area rather than just running straight to the boss. On occasion, the host may also have come in from the Valley of Drakes and wants to backtrack through the upper levels as well, so be familiar with the entire area.
Ceaseless Discharge:
Summoning Efficiency: 2 (1 above level 150)
Recommended Level: 40-45
Pros: Easy fight if you have a cooperative host.
Cons: Poor and often random summon sign locations; impossible fight if you don't have a cooperative host. If the host is willing to sit back at the white light and do literally nothing while they let you exploit the various gimmicks of beating this guy, then it's no worse than soloing him. If not, expect the boss to mess around outside of your attack range due to unstable aggro, OHKOing you and then the host (or the other way around).
Iron Golem:
Summoning Efficiency: 3 (2 above level 150)
Recommended Level: 40-50
Pros: Simple fight for good amount of souls, and mandatory boss and viable summoning area right before the boss fog gate means frequent summons.
Cons: Sen's Fortress is a difficult area for co-op, this is one of only 2 bosses it is recommended that you put your sign right in front of the boss area, as the amount of tricks and player control required to get through the Fortress can actually be hindering to a host if a phantom is in their way of escaping a trap. If you prefer more of a challenge, it is not uncommon to place signs at the entrance to the fortress, although you will likely have to take a very active role in ensuring that various traps are avoided and that the host sees how to best navigate the swinging blades and other devices. Outside the fog gate to the Iron Golem, it is absolutely imperative of you as a summon to ensure that the Firebomb Giant up the adjacent stairs is killed, otherwise he will carpet bomb the boss fight and make your lives miserable. If you hear the explosions indicating the Giant is still alive and the host doesn't seem to be planning to go up and kill him, you should try and guide him there with an appropriate "Point Up!" gesture.
Crossbreed Priscilla:
Summoning Efficiency: 5 (3 above level 150)
Recommended Level: 55-60
Pros: If you know the area well and are willing to take a few shortcuts, getting to and beating the boss is a breeze. May also occasionally assist in killing NPC King Jeremiah, netting you even more souls than the boss itself.
Cons: Hosts love to explore this area. Expect every few hosts to wander around finding all the loot instead of going for the boss right away. Like the Depths, be ready to act as a guide if they seem lost. The tunnels and underground area filled with bonewheel skeletons are also notorious for surprising the experienced and inexperienced alike, so you may lose out on some boss runs due to the necessity of either seeing yourself slain to protect the host, or watching a host run from one wheel skeleton into a nest of other ones.
Dragonslayer Ornstein and Executioner Smough:
Summoning Efficiency: 5 (3 above level 150)
Recommended Level: 40-55
Pros: Easily one of the fastest summoning spots you'll find in the game within the right levels, and due to the types of enemies and the boss itself, is also one of the best places to co-op for souls. Common summon spots include at the bottom of the main stairs leading down from the elevator and before the large rotating staircase, in and around the second bonfire past the two notorious silver knight archers, and in the area leading up to the boss gate for those coming in once the shortcut is opened.
Cons: Toughest level to assist someone through if they haven't already opened the shortcut, as well as having the highest chance of getting invaded, so learn a bit of PvP just in case. Due to the amount of impact the order of killing them matters to the host, you will need to pay close attention to the host at the start of the fight on who they want to take out if they don't message you out of game first, as hosts will not like it if you kill the wrong one first.
Dark Sun Gwyndolin:
Summoning Efficiency: 0
Recommended Level: 40-55
Pros: Relatively high amount of souls given per kill, large level range as people will take him on before or after beating Anor Londo.
Cons: It is impossible to know if the host is going for this boss or not, as the only summon sign locations even near him are on the bridge after leaving the rotating tower two levels above his area entrance, and these spots are the ones used to help people through Anor Londo towards Ornstein and Smough. You can indeed put your sign here and be summoned rather quickly, just don't ever expect a random host to be running towards Gwyndolin.
Pinwheel:
Summoning Efficiency: 2 (0 above level 150)
Recommended Level: 20-40, 55-65
Pros: Arguably the easiest boss fight in the game, almost no special strategy required. Many players do not head to the Catacombs until they have the Lordvessel from Anor Londo and are planning to continue on to the Tomb of Giants, so it is not uncommon to be summoned well above level 40. PvP with invaders in the Catacombs can also be highly entertaining given the level design.
Cons: There is no good place to put your summon sign in the Catacombs, and very few people need help with him; this boss is commonly joked about with how people were able to kill it in 2 or 3 hits. Reaching him, however, can be more challenging due to enemies such as bonewheel skeletons, and it is possible to be summoned by leaving signs near the first or second bonfires in the catacombs, or on one of the main pathways.
Moonlight Butterfly:
Summoning Efficiency: 3 (1 above level 150)
Recommended Level: 15-25
Pros: Easy fight if you have ranged options.
Cons: Very few hosts actually need any help besides Witch Beatrice, so they don't look for summons too much. In addition to Beatrice, it is possible to be summoned if you leave a sign near the entrance to the area, or on the stairs leading up to the boss gate.
Great Grey Wolf Sif:
Summoning Efficiency: 2
Recommended Level: 20-50
Pros: Easy fight if you can manage to stay between the boss's legs, huge level range as people will take on this boss at many points throughout the game.
Cons: Be aware that most people that may summon you here are probably going for Forest Hunter PvP; if it weren't for this fact then the summoning efficiency would be closer to level 4. Putting your summoning sign close to the doorway leading to Sif can significantly increase the odds of being summoned by a host planning to actually fight the boss, although at the cost of less hosts reaching the gate alive due to high volumes of Forest Hunter and other invaders.
Demon Firesage:
Summoning Efficiency: 4 (2 above level 150)
Recommended Level: 55-60
Pros: Short trip from the bonfire to the boss area, decent souls gained from the enemies on the way. A powerful and frustrating boss for many newer players, Demon Firesage can also be a challenge even for experienced summons and defeating him can be fun and gratifying for all involved.
Cons: His huge AoE attacks can be a pain to deal with if the host is unfamiliar with them and can't dodge too well, be prepared to be hyper-aggressive to hold the boss's attention away from the host just in case.
Centipede Demon:
Summoning Efficiency: 5 (3 above level 150)
Recommended Level: 60+
Pros: The only boss to get reliable summons at unusual level ranges due to the reliance of the Orange Charred Ring in the fight; one of the shortest paths from the typical summon areas to the boss.
Cons: Takes a ring slot for the Orange Charred Ring, so be sure you're build isn't currently reliant on a 2-part set. At higher levels (about 90+), the efficiency lowers to be more around a level 4.
Bed of Chaos:
Summoning Efficiency: 2 (0 above level 150)
Recommended Level: 60-75
Pros: This is often a very annoying "boss"/minigame for many players, compounded by the challenging area and fairly common PvP invasions. As a result, if you are looking to do some good this area can be very rewarding, as hosts are extremely grateful for any assistance. Helping hosts learn how to quickly run from the bonfire to the boss fog gate can save them a lot of aggravation in the event of repeated deaths, and the PvP fights keep things interesting even if the ultimate boss battle is usually a study in frustration. The third invasion by Darkwraith Kirk occurs right near the fog boss gate, and generates a significant amount of souls for summons even if the party is later defeated by the boss. The most popular location for summon signs is near the second bonfire inside the small building, but being summoned at either the first bonfire past the Centipede Demon, or right outside the boss fog gate is also possible.
Cons: Fairly long run from the second bonfire to the boss room (although foes along the way can simply be avoided), and incredibly difficult fight to coordinate with someone who doesn't know what they're doing. Even if they do know what they're doing, chance of success is relatively low, and isn't boosted much by having a partner outside of breaking both orbs simultaneously. Hosts also often want to take two summons in with them, to maximize the odds against the boss. This can cause a fair amount of waiting at the bonfire while the host searches for other summons, and increases the likelihood of invasions.
Gravelord Nito:
Summoning Efficiency: 2 (1 above level 150)
Recommended Level: 60-75
Pros: Good amount of souls from his defeat, easy fight due to Nito's slow speed and weakness to pyromancies.
Cons: The Tomb of the Giants is a very frustrating area. The most popular location for summon signs is at the second bonfire, which at least ensures that the host has already had some experience with the various horribles in the Tomb of Giants in order to get that far. It is advisable to encourage the host to stick as close to you as they can and try to run your way through the remaining stretches, because if the host starts to freelance one or both of you will probably be killed.
Seath the Scaleless:
Summoning Efficiency: 4 (2 above level 150)
Recommended Level: 60-75
Pros: A good number of people want help to keep him distracted so they can cut off his tail. A popular location for summoning signs is at the final bonfire in the Duke's Archive, on the balcony. High volumes of PvP invasions can lead to fights with invaders in the Archives, the forest with the Crystal Golems, or all the way down into the Crystal Caves.
Cons: People who go after the tail tend to get smashed around by his tail's attacks without realizing how tough they can be. Expect a few careless hosts eating these attacks and dying. Reaching Seath can also be a chore if the host is overaggressive with various foes, or is encountering the invisible pathways for the first time. This is one area where summons should always take the lead.
Four Kings:
Summoning Efficiency: 4 (2 above level 150)
Recommended Level: 60-75
Pros: Very fast summons as many people seek help with this fight. Summons happen frequently at nearly all levels, up to and including 120+.
Cons: Odd sign dropping location, the best spots currently being either in large open area with the distressed hollows, or on the circular platform after the first wooden plank bridge just past the distressed hollows. Given the nature of this fight, chances of success, even with help, without careful coordination is relatively low.
Gwyn, Lord of Cinder:
Summoning Efficiency: 5 (3 above level 150)
Recommended level: 65-80
Pros: Very wide level range since many people reach the end of the game at different times, one of the best bosses to co-op for soul farming, simple and short path from the summon location to the boss. Given that the area is rather short, this is a classic example of where the host can make a break for the boss gate to ensure they survive the frequent invasions that happen in this area. There is a fairly good chokepoint for summons to hold off invaders that pursue right where the 3rd Black Knight stands on the narrow walkways halfway through the level. Just be ready to sprint to the gate yourself as a single host may not last long against Gwyn.
Cons: The Kiln is a PvP hotspot, so there is not a great location for summoning signs as those left at the beginning of the level are usually triggered for PvP rather than boss runs. Placing a sign past the first Black Knight or at the boss fog gate can sometimes work to better ensure being summoned for PvE, though you will likely have to wait longer to be summoned if you do this. Be prepared to use your Black Separation Crystal if you are summoned for PvP instead of PvE. This also means that at the higher levels, where PvP is frequent, should you find a host actually doing a boss run, then invasions from phantoms will be frequent.
Sanctuary Guardian:
Summoning Efficiency: 4
Recommended level: 30-40, 55, 80+
Pros: Relatively easy fight if you know the combos and have some patience, but the fight is never boring. Summons may help with cutting off tail since openings are small. Only 1 area to drop signs. The Guardian's attacks, notably his melee combos and flying lightning sprays, can surprise and kill an unprepared host fairly easily and without warning, even if victory seemed imminent.
Cons: His combos drain a lot of stamina, he has several punishing area of effect attacks due to his lightning use and the water-filled zone, and also has the ability to poison you. High mobility makes him difficult to fight with no ranged options, and it can be difficult rescuing a host if they get into trouble due to a tendency for the Guardian to fixate on a particular target. Players enter this area at very different stages in their playthrough (although it does require the Lord Vessel and access to Duke's Archives), so the co-op sweet spot can sometimes be difficult to locate on a given day.
Artorias the Abysswalker:
Summoning Efficiency: 5
Recommended level: 40-60, 100-120
Pros: Very entertaining and challenging fight, and many people want help due to his aggressiveness. He is one of the more difficult bosses to defeat solo, so demand for co-op stays high. The best location to place your summon sign is right outside his fog gate, allowing for very fast repeat summons between fights. This is also the preferred location to be summoned for Kalameet, so it is generally a great location for co-op due to the variety of possible fights, and the high co-op demand for help with both bosses.
Cons: Many signs are placed in front of fog wall. For hosts, making it there alive may be challenging if you have not activated the shortcut, and many players play through the Royal Forest in hollow form to activate the elevators before returning in human form to summon assistance. For summons, this means you are unlikely to be called on to deal with PvP or any other portion of the level, which can sometimes get monotonous after a while (although you can also get summoned up near the Oolacile Sanctuary bridge if you prefer to run the full level). Artorias is also a dangerous opponent in NG and positively deadly in NG+ and beyond, so co-op wipes are fairly common. If the host does not stay on the defensive or otherwise is unfamiliar with Artorias' moveset it is likely to be a short and painful battle.
Manus, Father of the Abyss:
Summoning Efficiency: 5
Recommended level : 40-60, 80, 100-120
Pros: Extremely entertaining and challenging battle particularly on later playthroughs, and it is routine to be summoned all the way up in the Oolacile Township before entering the Chasm of the Abyss, so there is a lot of variety in the zone. Manus is a lot of fun to fight co-op, and is one of the few bosses that holds his own even in the face of three experienced players plus Sif (who can be summoned for the fight if you saved him before). In addition to the Township bonfire, it is fairly common to be summoned at the second bonfire at the entrance to the Chasm, or on one of the main paths in the area.
Cons: Powerful attacks that can take out a character quickly. Be sure you have a Silver Pendant to nullify his Dark Magic attacks, as they are very difficult to dodge. The Township area has an extremely high level of PvP invasions as well as a number of dangerous computer foes, so getting a host safely to Manus can be a challenge. The lower Chasm of the Abyss area has reduced PvP invasion rates, but most of the computer enemies there give little experience and can make getting through the zone a bit of a slog. The Township and Chasm are also one of the worst places in the game to be gravelorded due to the number and power of the black phantoms that appear (including multiple extremely dangerous Chained Prisoner black phantoms), creating either additional co-op dangers or challenges depending on one's appreciation level.
Black Dragon Kalameet:
Summoning Efficiency: 5
Recommended level: 40-60, 80, 100-120
Pros: One of the best fights in the game for co-op, with an impressive and sometimes overwhelming opponent as well as a large open arena. Hosts routinely need help cutting off his tail, so make sure to have a weapon or other attack that can do the job. High magic resist is recommended as Kalameet's fire does magic damage. It is possible to be summoned right outside Kalameet's fog gate in the lower valley, but the most popular spot by far is just outside Artorias's arena (Kalameet effectively becomes the new boss of the area once he is shot down), so players can enjoy fighting both Artorias and Kalameet by putting their sign in a single location.
Cons: One of the toughest bosses in the game due to high health and some surprising mobility. Especially dangerous to a summon since he can inflict Calamity status and you cannot heal through conventional means. The fight can last a long time particularly when Kalameet is not being accomodating with respect to letting his tail get cut off, or if he is spamming flame attacks. The large AoE of many of Kalameet's attacks, combined with his many knockdown abilities, can also make the battle frustrating and very dangerous at times.
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Now use this to summon one another as spirits, cross the gaps between the worlds, and engage in jolly co-operation. Praise the Sun!
