Basically what happens when someone is really really emotional and incredibly powerful. She resurrected like 50 times.
A level 5 mutant, highest of its ranks. The Phoenix Force joins with Jean Grey often times uncontrollable. It is immortable and mutable manifestation. It is a child of the universe life and passion. It has the power to destroy and create a whole universe. Even though the Phoenix has many hosts, Jean is the rightful owner and most powerful when combined with her.
Comic: Adventures of Cyclops and Phoenix #2
Comic: Avengers #263
Comic: X-Men: Phoenix Endsong #2
Comic: X Men: Phoenix Force Handbook #1
She a Bad B****