From Halopedia, the Halo wiki
The Heatwave fires purple hardlight implosive projectiles in two different firing modes. When in the first firing mode, both sides of the front cowling are extended outward, and it fires six projectiles in a horizontal pattern. The second firing mode has the side cowlings retract inward to fire the six projectiles in a vertical diamond pattern. In both modes, the projectiles can bounce off of hard surfaces like walls and ceilings. Upon imploding, the hardlight projectiles can disintegrate organic targets, like many Promethean weapons.
The Heatwave does relatively low damage per shot to enemy players, but combined with its high rate of fire and unique alternate firing mode, is a formidable power weapon in the hands of skilled players.
A common strategy with the Heatwave is to combine a single shot with melee for quick kills. The weapon’s effectiveness is particularly dependent on how many bolts hit the intended target, as well as how far away the player is from the intended target.
List of appearances