Not that Magatha mentions it, but she hands players the Elemental Nullifier on accept. Animus is floating at [54.9, 63.1]
in the middle of the Twilight Withering. The nullifier has an 80 yard range, so pick a good spot and use it on him to make him attackable. He only has 2956 health, but the following abilities:
[Shockwave]—Sends a wave of force in front of the warrior, causing damage and stunning all enemy targets within 10 yards in a frontal cone for 4 sec. 2 sec cast.
[Tornado]—Creates a Tornado under an enemy target 2.19 sec cast. Summons a Tornado which triggers...
[Tornado]—Deals Nature damage to all nearby enemies, knocking them back. Instant. Hitting for ~670-770 every half second!
The name of the game is running away (no matter the direction) the instant he starts casting Tornado. It hits hard!
Aggro:
Animus yells: DESTROY!
At 75%:
Grows larger...
At 50%:
Grows even larger...
At 25%:
Looks like he's about to explode!
Kill him and loot the Doomstone to hand it back to Magatha.