It's earth eater. Everything eater (anything eater?) is from x-2, I think.

I'm not sure about the capture requirements, just go ahead and capture one of every kind of monster if you haven't.

And if you find him difficult to beat, you're not the first:P Maxed other stats + deathproof +rikku mixing two light curtains is a good place to start, though. Then you just have to wait for him to counterattack with flare everytime-_-