Halo Infinite's campaign has many objectives to complete and secrets to uncover. These range from main missions to advance the story as well as optional side missions. One type of side mission is to hunt down variant weapons such as the Unbound Plasma Pistol. .
You can find the unbound plasma gun in the same area as the tower to the northeast. To unlock it, you will need to defeat the high value target, Briglard. Once you have defeated Briglard and collected the gun, you can now commandeer it from any of your FOBs. The Unbound Plasma Pistol will fire a volley of plasma energy rather than a single shot.
Related: How to speedrun the first level in Halo Infinite?
Screenshot by Thekingplayers
Note that these high value targets and their weapon variants don't seem to spawn until you find traces of them in your database. Capturing FOBs will reveal more high-value targets and allow you to claim their weapon variants.
So while you'll be able to get to this location sooner, it looks like you'll still need to acquire Briglard as a target in your database before you can unlock the Unbound Plasma Pistol.
For more information on Halo, see How to activate skulls in Halo Infinite Campaign and Where to find the second skull location in Halo Infinite Campaign - Cowbell Skull on the Pro Game Guides.
