The Heatwave rifle in Halo Infinite is a powerful rifle that shoots waves of energy. These waves of energy incinerate enemies in its path. One of these powerful weapons is hidden in the Outpost Tremonious mission in the game. Here is where you can find the Heatwave rifle.
Outpost Tremonious is the third mission you will play through in Halo Infinite’s campaign. This mission starts shortly after you defeat Tremonious and ride the elevator to the surface of the Halo Ring. Once you exit the elevator, make your way outside by following the pathway through the outpost.
After getting outside, turn to the right and go to the side of where you came out from. You will see that there is a rather large area you can explore behind the outpost. There are a few grunts in this area that you can sneak up on. The most interesting sight, however, is the door embedded in the cliff in the far back. Walk up to it but be careful, there is an elite with an energy sword inside. Take out the elite and follow the hallway to a small room that contains the Heatwave rifle.