Voyager

Voyager was a shadowy figure who haunted the Sixth Doctor's dreams. He travelled on his "Death-ship" and the Doctor dreamt Voyager held him captive on it.

Biography
Voyager once travelled to Alexandria and opened the way for ships to time travel thither. Astrolabus took this chance and left Earth.

Astrolabus stole some charts from Voyager, who ordered the Doctor to return them, holding him responsible as a fellow Time Lord. (COMIC: Voyager)

When the Doctor caught Astrolabus, Voyager summoned a storm that killed the thief. (COMIC: Once Upon a Time Lord)