Marvel Universe

Externals, or High Lords, are a group of mutants who possess immortality in addition to their natural gifts. The immortality typically kicks in after their first death, "freezing" the External at that age indefinitely. After that, an External can only be killed by "severing the five branches", presumably a reference to removing their head and limbs. Despite the legends, Externals proved vulnerable to the Legacy Virus and to Selene's life-absorbing powers. Externals also have the ability to summon each other into their presence and, if an External successfully kills another, they will absorb the fallen one's strength. This will eventually reverse itself unless all Externals but one are killed.

The difference between Externals and High Lords was initially not clear. Some references made it appear the two terms were interchangeable, while others suggested one referred to the immortal mutants in general, while the other specifically referred to the cabal Gideon and Saul belonged to. However, Selene has described "External" as the default state, those who sit outside of the normal world, while a High Lord is one who has achieved true ascension to god-like levels.