My raid team and I already have it. It's called outbreak prime. It's basically a hawksaw archetype pulse rifle with a seeking swarm of particles that proc on headshots. The exotic perk is definitely on a internal cool down so you won't be getting constant Siva swarms on headshot kills, unlike firefly that procs on every headshot kill. In the crucible it hits for 25 to the head and 17 body. The Siva swarm hits for 4 damage each. Think of a Hunter's swarm grenade and you'll have an idea of how aggressively the Siva swarm tracks enemies. The seeking Siva will rarely be reliable enough to get you another kill as it's target acquisition is worse than the aforementioned swarm grenade.