troble with a mission to level up

i don't know WTF the final boss in forest cave regenerates himself while fighting with no other amikin around as support and it regenerates while hitting and his regeneration is more per second then my damage making it imposible for me to complete the mission to continue with the story and is very annoying because at this point I can't have equipment tier 3 and I use a amikin rating A at level 30 and other rating A at level 25 with adventage of type and a rejuvenex just before the last fight, and the mission wants me to take 5 eggs from this place. how???