Carmilla is a boss character encountered in the latter part of Castlevania II: Simon's Quest. She serves as a formidable obstacle for Simon Belmont on his quest to destroy Dracula.

In Castlevania II: Simon's Quest, Carmilla guards one of Dracula's remains. Players must defeat her to obtain this fragment and progress further in their quest. The battle against Carmilla is one of the game's highlights, as she presents a significant challenge to the player.

The character of Carmilla in Castlevania II: Simon's Quest is inspired by the vampire from Sheridan Le Fanu's Gothic novella "Carmilla." Like her literary counterpart, the game's Carmilla is a seductive and dangerous vampire. However, the game's version of Carmilla is more closely tied to the world of Castlevania and has unique abilities and motivations.