Out of the Abyss
This is a black slaad, illuminated with UV light (with eyes and teeth recolored in photoshop).
Slaads are chaotic toad-like creatures that inhabit the elemental planes. The D&D 4e Monster Manual entry has this to say about them: "As creatures of pure entropy, slaads exist to create disorder. Their hold on reality is tenuous at best. Their thoughts are clouded with maddening images, they seem aware of things beyond other creatures' perceptions, and they attack without provocation."
Black slaads are the biggest and baddest of their kind.