In the following chapter of our guide to Doom Eternal, we provide information about the rewards received after you complete all six Slayer Gates and collect all 6 Empyrean keys.
To collect the main reward you must first complete all six Slayer Gates, which can be found on the following maps: Exultia, Cultists Base, Super Gore Nest, Arc Complex, Mars Core and Taras Nabad. For each gate you will receive an Empyrean key. Once you have acquired all keys, return to the ship and head to the location shown in the picture above.
You will find a new weapon there - Unmaykr. This a high firing rate weapon, which shoots triple energy projectiles - a perfect weapon for killing demons. It uses the same ammo type as BFG 9000, therefore you must search for it and save it for some troublesome circumstances. It's an excellent firearm that can be used to defeat the most powerful demons in the game and works well against the last boss.