There's already a Thread asking for a Dark Star skin for Xerath and I totally agree.
The pursuer of power is destined to become a cosminc entity of dark energy and destruction.
This skin concept went through multiple variations (check out my artstation link for more).
The final version has a core inspired by cosmic clouds / nebulae instead of the usual glowy strings.
For animations I'd imagine the core to rotate slowly and the glow on the collar could radiate up and outwards, like energy coming out of a rift in space.
You can find my other skins and more stuff in my artstation gallery here:
As always, if you like it, give it a thumbs up and comment if you want to.