Big Oaf will spawn in the corridor leading to the next PQ. He's an even bigger Giant than the other ones, but he uses the same model. Like most heroes, he hits really hard and has a lot of hp, he also has an area effect stomp that sends all close to him into the air. Be ready to heal your tank/melee - the stomp does damage (about 1k), but also inflicts fall damage, making it a rather possibly attack. The fall damage can be mitigated somewhat by making sure the tank positions himself with his back to a wall and under one of the small goblin huts jutting from the wall. The tank will thus fly off, hit the hut, and fall back down, falling a much shorter distance.