Kill 15 Sra’thik attackers at the Niuzao Temple within 5 seconds.
The Sra’thik are a group of mantid invaders occupying most of the northeastern portion of the island where Niuzao Temple is located. Even the temple is swarmed by these insectoids and the Black Ox himself, Niuzao, can be seen defending the front yard.
How to complete Yak Attack
The achievement simply requires a perfectly timed pull of 15 Sra’thik mobs just as the Black Ox is nearby. You won’t be actually doing the killing, as it is nearly impossible to do such a feat with so many enemies. On the other hand, any mantid caught in the path of the ox’s rampage is killled instantly when the ox arrives and tramps on them. In short, just position 15 mobs where the ox will be running amok: the outer ring of the courtyard.
The ox is actually not a necessity when doing this achievement with a group of players. For instance, a group of five can simply grab at most three mantids (a good number any class can pull and still survive), rendezvous with the other players at an agreed location, and use all available AoE skills once all mobs have been gathered.
To count the kills as your own (even if the Niuzao does most of the damage), you have to pull the mobs with a spell or skill that does any amount of damage. (I previously rallied the mantids towards the celestial ox’s rampage path without damaging them. It didn’t count towards the achievement.)
Try not to pull the mantids towards a Niuzao Sentinel as the latter will distract the former’s attention and you can’t therefore pull them into the ox’s path.
As a mage I simply pulled via a fast mount. I was lucky enough not to get dazed from all those attacks from behind. If in case I did get dazed and consequently dismounted, I’d simply use Blink towards Niuzao’s path. He was still too far though, so I had to use Ice Block, Frost Nova, and Mirror Image to buy some more time until he arrived.