This is the final boss of Act 2. Immediately after defeating it and moving through the exit, you will begin Act 3.
This boss is resistant to elemental and chaos damage. He generally starts his attacks by spawning some minions and then teleporting out of sight. After a short wait, he will teleport right next to you. He likes to cover the ground with ice that will hurt you, and then fire a laser at you three times. The laser attack is pretty powerful, but if you keep moving it should miss (keep your flasks handy in case it connects). If you're close to him, he may also use an overhead claw smash attack. He will keep repeating something close to this pattern until you defeat him.