Icy Clutch of Stygia is a heroic tier feat.
Prerequisite: Tiefling
Benefit: Whenever an enemy successfully saves against ongoing damage that you imposed, that enemy takes cold damage equal to your Charisma or Intelligence modifier. The cold damage increases to 5 + your Charisma or Intelligence modifier at 11th level and 10 + your Charisma or Intelligence modifier at 21st level