The Destiny 2 Coup de Grace quest isn't the most challenging you'll encounter in Bungie's MMO, but there are some frustrating bugs (opens in new tab) that may be stopping you from reaping the rewards of defeating the High Celebrant in the Dreaming City.
But more on that in a bit. First we need to initiate and complete the mission that arrived as part of the game's first reset of 2021. So, let's get started with that, plus what's known about getting around those pesky end-of-quest glitches so far, to help you claim the Destiny 2 The Fourth Mark ship.
How to start Coup de Grace in Destiny 2
You can pick up Coup de Grace by getting the Improved Speaker II lure upgrade from the Crow in The Tangled Shore, so long as you're at least reputation rank 7 with him. Once you've upgraded your Destiny 2 Cryptolith Lure (opens in new tab), speak to The Spider and configure your lure with the Prey Mod: High Celebrant.
From there Coup de Grace will activate, and you'll be prompted to head to the Dreaming City: You've got the High Celebrant to hunt.
How to defeat the High Celebrant
Start the mission by following the mission marker to the Cryptolith and, once there, activate your lure to spawn the High Celebrant. Now you can get some small damage in on it via the Wrathful buff (just stand in the green pool after killing the right enemy), but it won't be enough to take it down right away. For that, you'll need to follow the green goo on the floor to chase your target into the interdimensional nothingness of the Ascendant Plain.
Here you need to shoot the black orbs that take you to each new area so you can continue your hunt. If any of the black orbs don't take damage when you shoot them, the mission may be bugged, so you may need to restart. After a bit more running, jumping, and battles with smaller enemies and an easy-to-beat Wrathborn Ogre, you'll need to boot up the Cryptolith Lure in the Dreaming City, and then go back to the Ascendant Plain via some floating platforms that appear.
Now you'll face the final fight against the High Celebrant, which is pretty simple (although Anti-Barrier mods will be useful against the Barrier Champions), but be careful before you start unloading space lead: Bungie has warned (see below) that dealing too much damage to your enemy too quickly could be contributing to the quest reward not dropping, so keep reading if that's happened to you.
Players who are experiencing issues in the Coup De Grâce mission are advised to slow down when damaging the High Celebrant. Players should also wait a few seconds before shooting the black blight orb.January 6, 2021
Destiny 2 The Fourth Mark: What we know so far
As Bungie Help advised on Twitter, killing the High Celebrant too quickly could be a factor in the quest's reward, the rare The Fourth Mark ship, not flying into your inventory at the end of Coup de Grace. Even though it's not known how long specifically you need to wait, since the fight isn't especially tough, just try to take your time in defeating your enemy to make sure you get the ship at the end.
In other words, you should automatically get the reward once you've felled the High Celebrant; This isn't intended as something you need to grind for on multiple characters. And with that, best of luck—I'll update this guide once I know more about the elusive Destiny 2 Coup de Grace quest reward.