The Locus of Communion is the final boss in the Presage mission in Destiny 2. It is an interesting arena fight with some simple mechanics you will need to take advantage of if you want to finish off this enemy and get your hands on the Dead Man’s Tale Exotic Scout Rifle.
The fight will begin with the Locus of Communion appearing in the room, and spawning in multiple enemies with him. Damage the Locus until he disappears. If you look at the floor you will notice that many of the tiles under your feet are glowing orange.
The Locus of Communion has teleported below the floor, into an area that is too hot for you to follow. The only way to progress the fight is to cool down the area and follow him.
You will need to interact with three different consoles to activate coolant pumps to chill the floor below you, then you can drop down between gaps near the wall and take the fight to the Locus.
The first pump is at the far end of the room, behind where the Locus spawns. It takes a little while to activate, so make sure there are no enemies near you.
The second pump is located in its own room. If you turn around from the first pump, you will see it to your right. You will need good resilience, or a way to heal, when inside that room, as it will be hot and you will take damage over time.
The third pump is at the far end, where you originally entered the room. When all three are activated, the level below you will turn blue, and you can drop down and fight the boss.
Be careful down there, he does a lot of damage, including a ground smash that will one-shot you and leave a massive trail of fire. Damage him until his health bar is one-third of the way gone, and then the heating will turn back on. You need to jump back up to the other level and rinse and repeat the mechanics until he is dead.
The Locus of Communion will always stay near the last place you fought him until you drop back down again, so take advantage of this by dropping down onto the far side of his location, buying yourself space to do a lot of damage while he closes the distance.