Every 30 seconds Marrowgar will execute Bone Storm. This whirlwind attack cannot be avoided, and damage is dealt every two seconds based on your proximity to the boss as he spins. The closer you are, the more damage you take. Additionally, in heroic this will also leave a bleed effect on anyone hit by it.
While in his Bone Storm Lord Marrowgar will randomly target and charge a raid member. When he reaches them he stops moving for around six seconds before targeting another random raid member. Every time Lord Marrowgar reaches his target and stops he will fire four lines of Cold Fire along the semi-cardinal points (NE, NW, SE, SW - they form an X). Unlike during phase 1, the cold flame lines start directly underneath him. After his fourth target the Bone Storm will end.