EO3 Sea Quest Tier List

All of these assume you are at level. If you are overleveled, then in most cases the best option is the solo one since you can just brute force your way through the fights most of the time.

Meregho Saeno
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Best: Trio
Why: They can easily carry a starting team if you take this sea quest as soon as possible.

Worst: Solo
Why: Kirikaze is kind of there, and unless you've done some hardcore grinding or just waited to tackle this Sea Quest, your party is probably weaker than the NPCs available, and you'll likely want them to carry your team at this point.

Cruel Roamer
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Best: Solo if party average damage is decently high. Trio if that isn't the case, and your party has good elemental AOEs.
Why: For the solo, Bergman's Cow has very high average damage and will likely disable most of the mobs in the first two waves, and has a good chance of disabling Cruel Roamer in the final wave. For the trio, the NPCs have very high average damage and will straight up adapt their chasers to your damage type if needed. A proper setup can 1 to 2 turn clear the first two waves.

Worst: Duo
Why: Agatha's damage output is fairly low, and Giles' support is very lackluster.

Hammerhead
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Best: Solo
Why: Drake can disable and shut down the boss with his disables (which Hammerhead is susceptible to.) He can also contribute some decent average damage with his chasers once the boss is locked down.

Worst: Trio
Why: Low average damage compared to the other 2 Sea Quests. Which is a massive downside if you aren't allowed to bring along that much of your own party. And with this being a trio, that is the case. Also Victoria prioritizes supporting her allies over yours.

Ghost Ship
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Best: Duo
Why: Dezerte provides some fantastic support by healing your party with Protect Order and Reinforce, while wiping the debuffs the Ghost Ship places on you, and periodically wipes Ghost Ship's evasion buff. Toma himself isn't particularly helpful, but he functions as Dezerte's battery, allowing her to support you if the fight goes on for a long time.

Worst: Trio
Why: Low average damage. Also the NPC party members are rather frail.

Corotrangul
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Best: Trio
Why: Mito will actively support your party, as well as contribute some damage himself. Skaide will actively defend your party, though she is a slightly unreliable ally. Kirks' elementals can deal some nice damage to Corotrangul and kill the Bolt Strikers without activating their death counters.

Worst: Solo
Why: Laura is basically worthless as she is an offensive Hoplite and will never actually defend your party.

Golem
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Best: Solo
Why: Bongaro is the only NPC who isn't actively suicidal, and his AI cheats and will avoid having him attack Golem on turns it activates Reflection. He also contributes some good offenses. Note that he will never heal your party.

Worst: Trio
Why: ACTIVELY SUICIDAL! Their AI input reads Golem, and will have the sisters cast their elementals on Golem whenever it puts up a Reflection most of the time, basically killing them. Not only does this heavily tank your party's average damage, this also forces you to bring a dedicated reviver to the fight in order to keep up your party's average damage.

Manticore
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Best: Duo
Why: The NPCs have cheating AI, healing you at extremely opportune times.

Worst: Trio
Why: Low average damage, resulting in a fairly lengthy fight.

Ruin Caller
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Honestly just pick whatever suits your party best. All the NPCs will try to work with you, and bring a ton of crowd control to the table to keep the Ruin Caller under control.

King Penguin
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Best: Solo if using the exploit.
Why: If you're using the exploit, you'll get a fairly quick kill and be put in absolutely no danger.

Otherwise just pick whatever. King Penguin is pathetic and can just be DPS'd down very easily without putting your party in danger.

Scylla
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Best: Solo
Why: If using the exploit, you get a very quick and easy kill. If not, Solo just provides the best support out of all the NPCs, as Glaukos' Tiger serves a very nice meatshield and dishes out some nice counterattack damage. Glaukos himself also provides some nice support with his debuffs.

Worst: Triple Farmer
Why: Self-explanatory.

Leviathan
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Best: Trio if using the exploit. Duo otherwise.
Why: If using the exploit, you can get a very easy kill in the trio. However this requires bringing your own Wildling, as one is not provided for you in this party. For the duo, Dezerte is a semi-reliable support, with providing some good buffs and being able to dispel Leviathan's Fuming Snort debuff. And Toma serves as a decent healer. However Dezerte doesn't really care about the back row at all, so keep that in mind.

Worst: Solo
Why: Squire is an incredibly unreliable Hoplite. So much so that you're far better off bringing your own instead.

Elder Dragon
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Best: Duo
Why: Bergman hard carries you to victory with his animals, since they will keep Elder Dragon constantly bound. Also comes with the bonus of not having to bring your own Wildling just to stand a chance in this fight. Toma also serves as a gigantic battery for your party, keeping everyone's HP and TP topped off.

Worst: Trio
Why: Low average damage, and the NPC allies are terrible at inflicting binds on Elder Dragon. You are basically forced to bring your own Wildling just so you don't die to Supernova and have your damage tanked by Elder Dragon's damage halving passive. Resulting in a rather long fight due to lack of high average damage.