Holo-drone

Holo-Drones are small, mobile, spherical drones capable of remote use, using anti-gravity generators for propulsion, used for the creation of high-quality holographic images. They are used for several functions, allowing face-to-face communitation over relative short distance , providing holographical duplicate decoys of important personnel, and engaging enemy forces without risking allied personnel.

Sesa 'Refumee, the Sangheili leader of the Heretics based on Basis and a gas mine on Threshold, used one of these to taunt a Covenant Special Operations assassination team, and later used another two to assist him in battle as he tried to kill the one sent to kill him, the Arbiter.

They are relatively weak in battle, and a direct shot will result in static washing over their form, betraying their holographic nature. Though they possess rudimentary shields, and are somehow capable of using actual weapons, they don't seem to be dedicated combat equipment. Physically, they resemble unactivated plasma grenades able to slowly fly through the air, though slightly larger.

Trivia
There is a way to look at the Holo-Drone before Sesa 'Refumee uses it in the room with the four pillars on the right and left side. First when you start the level The Oracle go to the room with 4 pillars on the right and left side, jump on the pillar that is closest to the glass tube leading to a small square room in the center in the room, break the glass and jump on one of the four holes in the outer part of the square to get in, try not to fall, then inside its dark but there are four glass windows on the top of the square break one of them and jump(Crouch jump, Grenade jump recomended) on the edges, then you can see another room on top of the square, when you jump to get there, there are 2 holes on each of the four corners two corners with have pillars to help you get to the hole, but the other two don't so you need to grenade jump to it. You will find it floating