Cyberdisk Wiki entry
This miniature flying saucer is an automated terror weapon armed with a powerful plasma beam. The anti-grav propulsion gives it a big advantage in difficult terrain. Its primary function is destruction and terror in the service of the Sectoid race. If a cyberdisk is destroyed, roll above 7 on 2D6 to seee if they explode, with the force and range of an alien grenade.

The Cyberdisc is the dedicated Terror Unit of the Sectoid, and will only be seen accompanying them. It is a mechanical floating disc, comparable in size to our HWP, though it has a lower profile. It has moderate mobility, and can float at any level above the ground. It attacks with a devastating plasma shot, capable of firing up to three snap shots in a round with good accuracy and reactions superior to our HWPs.

It is resistant to armor-piercing weapons, and holds up well against psionic manipulation. Its slim profile can make it a difficult target for an object of its size. Worse, when it is destroyed, it usually explodes with a ferocity comparable to Alien Grenade or worse. New commanders often have difficulty destroying it with Terran weapons; it is advised to direct as much firepower as is available against one. Alien weapon technology is far more suitable for destroying it.

Commanders should remember that any mission involving Cyberdiscs will also involve Sectoids with Psionic capability. However, not all missions with psionic Sectoids will involve Cyberdiscs.