Appeared the first time with Summer Update 2008. He is a random spawn with no announcement.
Damage Taken From Elements
Stonecracker spawns near the stairs which lead to the Behemoth Quest room. It's also possible that it spawns after the level 30 door (as shown in the image) with 3 Behemoths. There were rumours at one time that it dropped Earthborn Titan Armor which appear to be false.
This boss behaves similar to a Behemoth, only with stronger attacks and the ability to heal itself.
Fairly easy for a level 80 knight to block.