The Five are 5 special mutants whose abilities work in concert to bring back mutants who have died in the line of duty.
Egg, formerly known as Goldballs, produces one of his gold balls, which turns out are actually eggs.
Proteus, inhabiting a cloned body of Xavier, warps reality to make the egg viable so a DNA sample of the mutant can be injected into it.
Elixir uses his ability to control biological processes to start rebuilding a clone body from that DNA sample.
Tempus uses her ability to control time to make the cloning process go much faster.
Hope is there to make sure their powers all work perfectly in unison at the peak of their strength.
Once the body is formed, Xavier uses his telepathic ability to input the copy of the fallen mutant's consciousness that he occasionally backs up to an organic server.