Doctor Strange: 11 Giant Questions It Leaves Unanswered
9. What Happened To Kaecilius?
The Question: After Kaecilius is recalled from Earth by Dormammu, he is shown traveling to the Dark Dimension along with his zealots, where he appears to mutate into a grey husk of a being. What exactly happened to him? Is he dead or what?
The Likely Answer: No, Kaecilius doesn't seem to be dead, though it seems hard to really call him "alive" in the traditional sense given how drastically he was mutated by Dormammu.
Comic fans might've noticed how Kaecilius' final form is rather reminiscent of Strange's frequent enemies, the Mindless Ones, extra-dimensional creatures with no will of their own who are manipulated by other, more powerful entities.
In short, Kaecilius is probably wishing he was dead right now, destined to be a soulless husk at Dormammu's command forever more.