Vote: Sanguine Inquisitor
Aside from the fact that it is my entry I think it fits the theme of Gothic Horror with its corrupting nature, blood themed powers, and its medieval templar flavour. These together make it slightly lovecraftian, especially in addition to the Whispers in the Dark ability. The mechanic's seem sound and in the upper area's of tier 3.

MLTSP: The Gray Men
I can truly see myself writing a horror and intrigue campaign with this creature being the man behind all the problems. A living idea of doubt, mistrust and curiosity. This would be a great Eldritch Abomination to send against my players.