Rift energy
From Tardis Wiki, the free Doctor Who reference
Rift energy was energy derived from temporal rifts. In an alternate timeline created by John Hart, he used distilled rift energy to cut Jack Harkness off from the Time Vortex, nullifying his immortality and transfering it to himself. Jack, however, remained a fixed point in time, and his eventual death resulted in John's universe collapsing in on itself. (AUDIO: The Death of Captain Jack)
