I have no solid ground to stand on, so take this answer or leave it, yours is just as good as mine However, Fireteam tuyet stumbled across something in the vex network before they were killed/(whatever vex do to people to make them lost in time) and in the ghost fragments of the vex, it talks about a group of people stuck inside of a vex simulation who call out to rasputin to try and escape this simulation. Dr shim was one of these. There's a bunch of blanks, however pocket infinity talks of how it found in the vex network the ability to create a time loop and fire immediately. It doesn't have Dr shims name, however I don't think it's a coincidence, that 1. The fireteam called out to a warmind, and the gun has rasputin written all over it 2. It holds a vex secret of time loop 3. Dr shim has a protocol to eliminate invaders from his archive..