Stetmann created the stetellites after his successful terrazineharvesting operation on Bel'Shir. He created them as a cross between zergcreep tumors and protosspylons. Gary could overcharge the stetellites in order to give greater buffs to his allied mecha zerg. Their fields could be modulated between three different modes: Fun Accelerator for Speedy Transportation Configuration, Health Uptick Generating System Configuration, and Just-in-time Uninterruptable Input for Charging Egonergy Configuration.
Stetellites are the central mechanic for Egon Stetmann in Co-op Missions. They spread an area of egonergy which gives various buffs to Stetmann and his ally's armies. The spread of stetellites gives Stetmann's army an edge, and Gary's abilities interact with the stetellites. Stetellites are not destroyed when attacked, but instead go into a "deactivated" state for 30 seconds. Stetmann can only place stetellites in the power field of another stetellite or larva-producing structure. Stetmann's units that die in near stetellites are "recycled," and count toward respawning a free unit of that type.
Stetellites can be set on three configurations. FAST increases movement speed of units under it, HUGS provides massive healing to nearby units, and JUICE provides energy regeneration, and is the only way Stetmann's units can recharge energy. Gary can overcharge the stetellites, giving an attack and movement speed bonus in FAST, a shield to nearby units in HUGS, and a burst of energy regeneration in JUICE.
The rate of which Stetmann can spawn and store charges of stetellites depends on his highest tier hatchery structure. Mecha hatcheries allows Stetmann a total of 3 stetellite charges and a 25 second cooldown, mecha lairs allows a total of 5 stetellite charges and a 20 second cooldown, and a mecha hive allows a total of 7 stetellite charges and a 15 second cooldown. When the lair and hive are first spawned Stetmann will instantly be given two stetellite charges.
On top of overcharging, Gary's abilities interact with the stetellites. He can teleport himself and any surrounding allies to any active stetellite on the map. When in a stetellite field, his E-Gorb ability spawns three orbs instead of one. When in Super Gary form, Gary can generate his own egonergy field, allowing Stetmann to spawn stetellites within it far beyond the initial cluster of stetellites if needed.
The concept of how Stetmann would utilize energy fields was something established very early on in his development, and remained unchanged through his development. The Co-op Missions team experimented on whether stetellites would be invincible, cloaked, or destroyed when targeted by enemies, finally settling on having them able be permanent but temporarily deactivated when attacked. Other proposed ideas were stetellites with more hitpoints, as ground units, or that functioned similar to sensor towers.