What's a Wither?

About to start on my New X-Men issue, so I figured I'd get familiar with the characters. Here's me trying to get used to Wither. I don't know if I've got a haircut I like down. His is kinda shaggy (sort of similar to Chase in Runaways, but not as drastic). The hair is a big deal for me a lot of the time, because it can ruin the way the rest of the face looks. Maybe I should worry about bigger things, I guess :)