Looking for Monster

[Nodsiu]

Its like a big lizard, but made of shadow. I saw it before but can't rememer what book it is.

[Mike Miller]

Perhaps the dusk beast from MotP?

[Waker]

Perhaps the Black Slaad?

[Zaq]

Do you remember the approximate CR, or maybe anything about its abilities? Was it an unintelligent brute? A cunning manipulator? A sack of HP with very little to distinguish it from any other magical beast? A terrifying supernatural monstrosity that can overwhelm an at-level PC by getting the drop on them? Something else?

If nothing else, you can always slap the Dark and/or Shadow template(s) on a drake or a dragon or something, but I don't think that's what you were looking for.