Various floating robot enemies created for CITY OF HEROES: GOING ROGUE.
Praetorian Police and Imperial Defense groups typically spawn with a few troopers and 1-2 of the corresponding support drones.
I'm quite fond of the Monitor Sphere: like other characters in Praetoria, it starts off innocuously enough but becomes a lot more aggressive when attacked. The Sphere actually shifts the color of its lights and pops out a series of cannons (!).
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Check out my dedicated concept art gallery here:
[link]
I like the closed and activated versions.