The minimum level required is 250 to start Feaster of Souls, but it's very hard. The recommended level is 300-350 for mages. Even if you pay for a service, the minimum level they require for all vocations is 300+. And this only applies to mages.
Knights needs to have atleast level 400 or 450 to be able to block it, but they ask them to be 500+ and it's still risky. I've seen level 800 Knights dying while trying to survive, because the monsters hit very hard and if you lose a turn without Stone Skin Amulets and Might Rings you can't block the damage.
Paladins also take very hard hits and needs level 400+ to do it, but they also recommend being level 500 to use boosted Strong Ethereal Spear (Exori Gran Con) from the wheel of destiny to boost it's damage by 380%. If the Paladin is level 400, he doesn't have the boosted damage, otherwise, if he has this spell boosted, he practically carries the team on the quest.
Monks have the hardest time doing the quest because they can also die very fast trying to come up close and doing melee damage, they can be one-shot and If I remember right, they have the same level requirement as Paladins. On my world (Retro Open PVP) the service with a Monk failed like 5 times trying to do the quest because the Monk damage couldn't keep up with other vocations, also because he can't participate well considering he has to be almost all times at melee range and that makes him take more damage than the vocations who stay shooting from a distance (Mages and Paladins). I would also say that the recommended here is level 500, but maybe it can be done with a level 300 Monk considering he won't take damage from the team like it happens on Retro Open PVP servers.
Mages (Sorcerers and Druids) needs atleast level 300, I've heard that people completed it with level 250 mages (the secondary druid for example) and being carried by level 1000+ which can still complete the quest even if the low level dies, but it's too risky. When paying for a service, they will only accept it if the lower level is being carried by a powerful party with 4 level 800+, letting that spot open for a low level, but they don't like to do with a lower level than 300, because if the party fails a boss, it can only be tried again in 20h, and for them is a waste of time trying day after day since they mostly focus on doing all their services in a single day. Of course even with the suggested and recommended levels they can fail, I've seen a lot of times the Paladin dying with level 400+, the Knight dying at level 500+ or sometimes the Mages get one-shot and they need to try again at the next day.
It's a hard quest, created for higher levels, so it's expected that even higher levels (800+) can struggle while doing it. Even if you pay for a service, try to level up as much as you can to maximize your chances of success.
