New Starting race "Silvermist" !!
Once they was generated from an ancient race to terraform new planets, but these race ascend to a new level and vanish from the universe.
The Silvermist don't got a control anymore and repeat their last order, they still terraform but at their unique way, they remove all kind from civilisation they find.
On a replication process there comes an error/mutation into the code. These single Silvermist transform from a simple scripted robot into a real AI.
Now these new Silvermist can control it own destiny.
A Hive/Breeder/Control a big Silvermist who act as Starbase. Only place to create new swarms.
Harvester, who eats any kind of resources from any sources to grow up. Once they are at full size they head back to the hive and dump 50-90% of their size into the hive. Alternativ they just act as (Gas) Miner and mine and transport the resources to the hive and the hive grow with these resources.
Fighter, the start at max. size or 90%, much faster sublight speed then harvester. They regain size from eating ships, and they can maybe slowly get size when they are close to a sun.
Queen, like colony ships to create new Hives.
Research, to increase shipspeed, hyperspeed, size, firepower. and gain some new abiliys like Energy->matter to heal at Sun, Shield, and new weapons. And some ultimate reseach goals like Replicants the AI transform from a Swarm AI into a single body and basicly could create a regular empire as Race Mechanoid.