Magik has always skirted the line, and the Phoenix Force just pushed her over the edge. Wielding her flaming Soulsword she punishes any Heroes around her. If she manages to KO a Hero, they are instantly banished to Limbo and must be replaced by a new Hero. If 4 Heroes are banished, she is victorious.
With her Threats, Magik brings the Limbo realm in close proximity to our reality. Limbo Demons help her attack the Heroes, and Limbo Prisons make Civilians harder to rescue and hold back the Heroes trying to move. The demonic interference can become so strong that Heroes are prevented from using their Special Effects. Playing around in Limbo, Magik can force all Heroes caught next to one of her Threats to discard 1 card.
https://www.kickstarter.com/projects/cmon/marvel-united-x-men/posts/3168479