Doctor Strange: 31 Easter Eggs & References You Must See

Kaecilius is actually a villain from the comics, though an unexpectedly minor one. He was originally an ally of Baron Mordo - an underling of the former Ancient One's student, which is alluded to when Mordo tells Strange that "stronger men than you have lost their way."

In the film he's actually more like an amalgamation of several characters: he's based at least partly on the traditional presentation of Mordo, as well as black magic wizard Kaluu and his master Dormammu.

It was suspected that Kaecilius would be possessed (hence his eyes), but that is in fact just the mark of frequent dark magic use.