He drops Massive Kyparite Core which is a hidden daily quest for 130 Klaxxi rep. He only spawns the day dailies are open on Zan'vess. Like all quest mobs, he's able to be tagged by everyone.
He has 2.4 million health. When he burrows he takes 75% less damage, is unstunable, and makes spikes come out of the ground. Every time he surfaces from Burrow he takes 25% extra damage. Use his burrow time heal and build up whatever you can to burst him as soon as he surfaces as he doesn't stay surfaced long. Very easy to solo.