does anyone know where the obsidian is

[heylisen]

cant find it

[Nikolaus]

I assume you mean G-Rock (Glassrock). You can mine it in the Mourning Fields, the biom in the Underworld immediately after Oceanus.

[heylisen]

in french its obsidian its for the skull

[BigAlzBub]

It is really rare, and can be hard to find because of the open nature of the levels.