The Master was an Overseer upgrade with three minion spawners. It could spawn 6 minions (Factory drones), but the were uncontrollable AI minions. The Master was subsequently succeeded by the modern Factory design, which, as I'm sure you know, has controllable minions spawned from a single spawner
This reevaluation of the original Master brings something new to the playing field, and could consequently revive this old class while still maintaining the original's main concept. The spawners can spawn one minion each, meaning you have 3 minions (instead of 6). The difference is that these minions have no controllable movements. The movements of the minions are instead directly tied to the Master; they will orbit slowly around the Master after creation, similar to how an Auto 3 / Auto 5 auto spins. This class is actually more similar to the Auto 3 than the Overseer. Minions are free to target whatever they want like Auto Turrets do, and do not have the angle restrictions like the Autos' side mounted turrets. When using LMB, all your minions will shoot at your Cursor. In addition, minions can deal touch damage and (probably accidentally) block shots.
Master minions have 20% increased Drone Health, Drone Contact Damage, and Bullet Penetration stats compared to Factory Drones and may attack anything a normal Auto Turret can, but are otherwise identical to Factory Drones albeit with restricted movements. Stat titles for stats   and  are "Bullet Speed", "Bullet Penetration", and "Bullet Damage" respectively, and not "Drone ---", even though increasing Damage and Penetration will also increase Drone Contact Damage and Health. Increasing Bullet Speed will not increase Drone Speed and thus have no effect on minions' orbit. Minions do not receive any recoil effects from their barrels and cannot be moved from knockback when hit; if they received either, the Master itself might be effected by the resulting minion movements as minions' position is directly tied to their Master. A Master is not rotation locked like an Auto 3 is, so feel free to spin or screw with minion patterns.