The Play’s the Thing
(Complete the Taken King main Questline, culminating in Regicide. )
Complete Destiny: The Taken King’s primary story. You don’t have to complete the raid for this particular Triumph, although you do need to for one of the others. Simply play through each story mission until you have to face Oryx on the Dreadnaught (this mission comes after you steal Crota’s Souls to become Ascendant. If you’ve had this expansion for some time, then chances are you’ve already accomplished this task. But just in case you haven’t, here’s a quick rundown of the fight.
Defeating Oryx in this mission is nothing like when you face him at the end of the King’s Fall raid. Oryx will teleport around between the platforms, making it a bit difficult to land shots on him at times, but if you’re working with your team you’ll be perfectly fine. If you happen to be playing solo, just use patience, and make sure to wipe out the constant waves of adds this boss sends out.
At certain points in the fight (based on how much damage you’ve done to Oryx), you will be transported to an area surrounded by mist where Taken will appear to fight you. Kill the Taken in order to draw Oryx out of the mist’s protection, opening the foul beast up to your damage.
Just rinse and repeat until he falls. Collect your triumph and move on to the next challenge.