Eats your Legs. Does 45% damage instead of the normal 10% after being killed by him
This is a triggered spawn using the items given to you from the hailable Froglok in the zone (the one you open up via the weapon rack).
He spawns in the center of the same room that houses The Elemental Warder.
Common method for tanking him is to pull him to corner of a hallway and have all your dps within 10 meters. He has a small Memory wipe, the closer he is to your tank the better off you are. Healers are then standing across the hall a little ways down wedged against a pillar to prevent the small knockback.
With about 7-8k poison resist the AOE's should be very manageable for your raid force.