Arcana gameplay of the dungeon.
1st boss does the circle with shots out twice it can go around him or around the room either way just run in a circle. The 2nd time you will get marked and shots from the sky come down where you're standing. Obviously you want to drop them near the wall so it's easier to run (common sense but some put them in the middle anyway).
2nd boss just fight her until about 10 health bars then she does the circle and you're to collect 3 yellow orbs and avoid red ones. Each person takes a section to cover and destroy the orbs floating to her with the buff otherwise a 1 shot mechanic occurs. At some point during the fight she will charge up and needs impaired to interrupt it.
Lost Ark RU abyssal dungeon