Its from Thaumcraft, theres like an obsidian cave system, its strange

If you can dig into the cavern under it there is a load of odd stuff.

it looks like maybe something from thaumcraft, unless it's corruption in mystcraft :/ hmm... interesting, i'll have to look around for one somewhere.
i'd like to re-iterate what jack9909 said, just post this on the forums next time, you'll get a lot more responses and information there.
thanks,
--EdoKara--

Oh ok

its a thaumcraft monolith u use goggles of revealing to find what crasyals to use to open it

Do you know the forum name

Try the forums next time. And look at the wiki... :P