Prometheus (Raid)

Binding of Caucasus

Even though Omen of CaucasusHeralds the coming of the Binding of Caucasus
bypasses VeilDebuffs will be nullified (1 time)
"Veil" is an unofficial name used by the wiki for this status effect. Its actual in-game name is "Immune.", Binding of CaucasusATK and DEF are lowered / Can't use charge attack or skills
does not. If you lack a clear for Omen of Caucasus, and are willing to receive the damage from the Goddess Flame trigger, using a Veil will block all the debuffs incoming, including Binding of Caucasus.

Main Character

Recommended classes for the main character include classes that can provide party sustain while still dealing damage, and those that can bring a multitude of Clears and Veils to deal with the boss's consistent casts of Caucasus after 75%. This makes Sage the strongest pick, due to its ability to bring two clears in the form of  ClarityRemove 1 debuff from all parties. and  Peace of MindRemove 1 debuff from all allies.
All allies gain Shield (500)Next ATK received will be ineffective for a fixed amount
Strength: 500Duration: 3 turns., bring  VeilAll allies gain VeilDebuffs will be nullified (1 time)
"Veil" is an unofficial name used by the wiki for this status effect. Its actual in-game name is "Immune."., and it can mainhand strong staves like True Glacial Dream Staff or Blue SphereRecommended at 4★ only. Other picks include Nekomancer, which brings strong offensive and defensive party buffs and has access to the same mainhand options as Sage, and Doctor for its similar access to Clear utility and healing.

Recommend subskills for the main character should aim to shore up whatever your team is lacking, but tend to focus on mitigating damage or preventing the boss's many debuffs, as surviving is the most important part of the fight. Attack and defense debuffs like  Miserable MistInflict 25% ATK DownATK is lowered
Strength: 25%Base Accuracy: 80%Duration: 180 secondsStacking: Dual and 25% DEF DownDEF is lowered
Strength: 25%Base Accuracy: 80%Duration: 180 secondsStacking: Dual on all foes., are always useful; however, it is important to note that Water has access to many strong debuffing characters who bring other utility to the fight, like Feower, Altair, and Drang, so the main character has less of a burden to bring debuffs on their own.  ClarityRemove 1 debuff from all parties. and  VeilAll allies gain VeilDebuffs will be nullified (1 time)
"Veil" is an unofficial name used by the wiki for this status effect. Its actual in-game name is "Immune.". are important for that reason.  Just the CureRestore 25% of all allies' HP (Healing cap: 1500). is a small heal, but is useful if you find it difficult to sustain as the fight draws on.

Summons

Recommended summons include a bare minimum of two fire Carbuncles. Either Garnet Carbuncle or Ca Ong. Given the long cooldown of Ca Ong and its smaller cut at 0★, it is recommended to prioritize the Garnet Carbuncle despite its lower stats unless you have several Ca Ong at 3★ or 4★. Since the fight is a marathon, two to three Carbuncles are recommended to maximize uptime on the damage cut to reduce the amount of incoming damage.

Other summons that have value in the fight include:
Bellringer Angel provides a 1200 damage ShieldNext ATK received will be ineffective for a fixed amount
and the ability to reset one of your other summon cooldowns if that shield is broken (excluding summons that cannot be recast like Shiva (Summon)) means that you can attempt to circumvent a third Carbuncle by using this summon's effect to reset the cooldown of one of them. It is also readily available in a Side Story, making it accessible to even with terrible Gacha luck.
Baal (Summon) and The Hanged Man (SSR) play a unique role here. 9 turns is a long time for a Clear to be used reliably, however if the main character becomes inflicted with Binding of CaucasusATK and DEF are lowered / Can't use charge attack or skills
, they can still call them to clear the debuff, freeing them from the skill seal. This works even at 0★, so you do not need to have a 3 or 4★ gacha summon for it to be effective.
Athena (Summon) is another option if you lack a third Carbuncle, providing a 30% damage cut at 0-3★, and a 30% Damage Cut and RefreshHP is restored on every turn
at 4★. Justice (SR) and Justice (SSR) in a sub slot will increase your maximum HP, and the call can be used as a unique heal that can pull low HP allies out of the danger zone. It is also a non-Gacha option, being obtained through Arcarum.
Morgana Car and Sandalphon (Summon) are both summons with healing calls that were freely obtainable through past events. The first has a Defense down debuff for the enemy, while the second has an Attack up buff for your party. Tiamat Omega at 4★ provides a single Mirror ImageNext one-to-one attack received will be ineffective
(Effect removed on next all-foe all-ally attack)
for your party, which aids in mitigating incoming damage.
Lucifer at 4★ has a massive 3000 heal and 30% Attack up that is always useful.
If a summon is not listed here, but has calls and effects the have similar roles, it is also useful. This is not meant to be a comprehensive list, so do not feel like you need to have all of these summons to clear the fight.

The Fight

Your damage will greatly affect how long this fight takes, but it is a balancing act of damage and your ability to survive. The longer the fight takes, the more consistent your mitigation and sustain will need to be. The opposite is also true, so strong grids that do high damage are likely to be able to get away with riskier strategies.

It is worth noting that Prometheus is a fight that becomes markedly easier when using a Varuna grid, since the grid is characterized by not only having high HP but high damage as well. This fight can also be RNG based, as she can often chose to target the same character for Caucasus several times in a row, making stretching the lifespan of a Veil harder and singling that character out to take more damage than usual. If the main character is your only source of clear, having them become inflicted with Binding of Caucasus can be run-ending, as taking multiple Goddess Flame triggers can cause damage and debuffs to add up faster than your cooldowns can prevent or heal them off.

Mitigation is key. As mentioned above, you want to have close to 100% uptime on Carbuncles, meaning 100% uptime on at least a 50% cut. Characters who bring damage cuts like Lily, Charlotta, Anre, and all Water versions of Katalina will always have a place, with Lily and the Katalinas being notable for bringing Clear and Veil respectively, as well as heals. Since Prometheus does not have any means to dispel your buffs, unlike many of the other 6 man raids, you don't have to worry about losing your Carbuncles at a bad time and failing the run as long as you pay attention to their duration.

Yngwie is notable for trivilizing the mitigation aspect if your grid can supply him with enough multiattack to keep his charge bar up and switch him into Tough Guy mode for Caucasus turns, since while he is in Tough Guy mode he has 100% Debuff Immunity and increased hostility, making him the prime target to draw away Caucasus, thus reducing a need for extra Clears and Veils.

Charge attacks to look out for mostly include her regular cast of Caucasus. From 75% to 25%, it will always cast on turns that are multiples of 3, like 12, 24, 33, etc. After 25%, it will cast on turns that are even numbers. To avoid taking more damage than usual you should be prepared to clear Omen of CaucasusHeralds the coming of the Binding of Caucasus
or you will take extra, unnecessary damage from the Goddess Flame trigger, or have strong cuts ready to mitigate taking several triggers in a row.

Sustain is your team's ability to weather damage and heal it off over the course of the fight. Damage can add up quickly, so all sources of healing are valuable, especially on a Varuna grid, since stamina plays a large part of your damage. Playing Sage with a 4★ Blue Sphere can potentially be all the healing you need, but characters who bring extra sources of healing like Arulumaya (Holiday), Lily, Lilele, and all Water versions of Katalina are options if you lack the Blue Sphere. Water has a great selection of characters who can bring healing and debuff mitigation, making them perfectly suited for this fight.

Sustain also goes hand in hand with debuffing. As mentioned above, there are many characters in Water who bring strong debuffs on their own. It is important to cap Attack down so you take less damage overall, and cap Defense down so you can end the fight quicker.  Miserable MistInflict 25% ATK DownATK is lowered
Strength: 25%Base Accuracy: 80%Duration: 180 secondsStacking: Dual and 25% DEF DownDEF is lowered
Strength: 25%Base Accuracy: 80%Duration: 180 secondsStacking: Dual on all foes. can lay the groundwork and be compounded on by characters like Feower, Arulumaya (Holiday), and Drang, all of whom also bring other things in their kits that will help make the fight easier, like Delay, Veil, and healing.

Saving the bulk of your damage or important cooldowns for the last 25% of the fight can be the difference between victory and defeat. It will be difficult to keep up with her casting Caucasus every other turn, so saving one use skills like Feower and Anre's fourth skills can help you burn her HP down faster.