Cthulhu Set, AEG 2013
The second expansion.
This one is Cthulhu themed.
It has a unique Madness mechanic, which meant designing a special Madness card.
The factions in this set are
Cthulhu Cultists, Elder Things, Innsmouth, and Miskatonic University.
Each faction has a unique card frame, font treatment, font color, and faction symbol.