Stele, plural Stelai, are small monuments most often seen in Segmentum Asia in the form of an obelisk with a wide foundation. It is a monument in civilian hands, used to mark a piece of territory or commemorate something important (latter one of the usage of the historical stele, as well as to mark borders). In military usage, it serves as a rallying point, as well as defensive point.
Military Stele are standardized, featuring a beacon to direct airborne supplies and weaponry to repel enemies with. Military Stelai are connected to a control center by default, meaning these aren't pure robotic entities. Military Stelai are armed and armored heavily enough to handle small scouting parties, but cannot hold anything greater without aid.
These are used extensively by the Hellenistic factions.