As Diego Navarro was on the run from the advancing Aurelian forces, during the Aurelian War, he escaped to Archelon Fortress with the remaining prototypes of Fenrir. Aurelia performed a short island-hopping technique to quell Leasath forces, including the elite Alect Squadron and the High-Powered Microwave weapon.
Reports differ from here on out. Some say that Aurelian forces concentrated on shooting down the members of Alect Squadron, allowing the HPM to be delivered to Archelon Fortress where it would then be outfitted onto the Fenrir and used to protect the fortress. However, others say that Aurelian forces first destroyed the HPM at Cobalt Cave before it could be delivered, allowing Alect Squadron to pilot the Fenrir aircraft.
Regardless of which report is true, the HPM was very likely destroyed at either Cobalt Cave or Archelon Fortress. It was never deployed in battle after these engagements. 
The HPM works as a standard heatseeking weapon that ignites fuel caught in between two opposing "plasma spheres," one emitted by a Fenrir and the other emitted by Archelon Fortress. An overlapping effect is created, which results in the plasma spheres.
The weapon was manufactured and created in Cobalt Cave, where satellites were placed to add a tracking capability to the HPM to make it easier to find and destroy aircraft. An electrical plant near Archelon Fortress powers the HPM (along with Fenrir's DOS system). 
- If the player escapes a plasma sphere before their plane is destroyed, their engine's temperature begins to stabilize. However, this wouldn't be the case in real life; the electronics within the plane, along with the engine itself, would be structurally damaged by the sudden, intense heat. The plane would retain some internal damage after escaping the sphere.