Effritus

Effritus is a rare gargoyle sometimes spotted near and road heading to Shadowfang Keep in Silverpine Forest. It is characterized by its grey and white skin.

Strategies
Effritus uses the ability Stoneskin that heals him for 240k Health over 6 sec. It's a 7 Sec cast, so you mostly have to burn him before he cast it or he'll be full HP.

Trivia

 * Effritus is most likely a reference to Islamic Mythological Character, a kind of devil.