I'm sure most of you have seen the old fixed way of doing this by leaving one or 2 people out of combat, and tanking him in the stairway then when get gets to 1-2% you die and when he runs back the ooc's players tag him and kill him.
We found a new way today after finding out that the old way was fixed.
We have all of our group stand on the opposite side of the entrance where you won't get into combat. Then we have a dps (preferably a rogue) aggro him and run up the stairs and out of the entrance (or die). While the boss is chasing him, he will transform into the mammoth. Once the player leaves or dies the boss will come back down. Now its time for your tank to grab him before he gets back to his pull spot. (make sure your dps that pulled comes back in or doesn't release)
He is now in mammoth form but since he is reset, it shows that he never casted his metomorphesis, and now you can kill him and get the achievement![]()