The Sergeant Sneaky combat robot was an advanced military automaton created by Equestrian Cybernetics in the latter years of the Equestrian-Saddle Arabian War to counter the similar battle droids employed by the latter belligerent. It was designed from the Sergeant Sturdy Common Attack Droid, but modified for ambush tactics and stealth missions. It features bladed weaponry, a poison dart gun, and an invisibility spell matrix.
Many are still active during the modern era, guarding Second Era sites. Lozenge is almost killed by one while exploring Charity Prime.
Source: Dirty Hearts
Source: In Oculo Venenum