Originally Posted by
Til
Hope is the key to resurrection. There was a datapage from Beast a while back that talked about it. Basically, in addition to boosting the rest of the Five and enabling them to work perfectly together, she also adds something they can't identify to the whole process. Because when they tried doing it without Hope, it didn't work. That's why in the Sins of Sinister timeline when resurrection was industrialized, in addition to clones of the other Five, each location needed a piece of Hope's flesh to make it work. That's also why they freaked out when she was killed in Immortal X-Men, because they weren't sure if Synch or Mimic using her powers would be good enough. It turned out to be good enough to bring her back, but notably it didn't cleanse her of Sinister's DNA imprint, which is something she did on her own for all prior resurrections without even knowing it.