Gideon was a member of the Externals, a unique type of immortal mutant, and an adversary of the X-Men spin-off group X-Force.

At the end of the 20th century, the group began seeking out their newest member, whom Gideon erroneously believed to be Roberto da Costa, a young mutant who had joined the New Mutants, the junior division of the X-Men, and taken the codename Sunspot Gideon had known Roberto from a young age, having business relations with his father, a wealthy Brazilian businessman named Emmanuel da Costa.

[5] When the young superheroes known as the New Warriors broke into his home while he was taking a bath in his Jacuzzi, Gideon defeated them in an impromptu skirmish with their combined abilities.

[7] He contacted Crule, and then gave Sunspot over to one of his scientific labs, where they experimented on him and augmented his powers (at the great risk of killing him).

[8] Gideon attempted a hostile takeover of Genetech and the Taylor Foundation, but was thwarted by Night Thrasher and was defeated by him in physical combat.

[14] Later while investigating a disturbance in the timestream caused by the premature death of Candra, Cable travels back in time and discovers that Selene's attack on the other Externals did not work as they thought, and that they were actually alive but being targeted by some unknown assailant.

Cable is confronted by the mysterious murderer, a time-traveling Gideon himself, who reveals that he spent 3,000 years in stasis and when he woke up, humanity had changed considerably.

Gideon was an External, meaning his aging process is greatly slowed and that he can apparently regenerate injured or missing cells from even near-fatal injuries.

He was granted with limited immortality, only ended by an extremely mortal wound such as losing the limbs, by the Legacy Virus (two Externals died by this method) or, in the case of his death, by a draining of the life energies.