The Droideka, or Destroyer Droid as it was more commonly known, was one of the CIS's most dangerous inventions, ranked up next to the IG-100 MagnaGuard. It was a type of heavy droid that was armed with repeating blasters and sports a personal shield generator that would protect it in heavy combat.
The Droidekas were more formidable than the Federation's more numerous B1 battle droids for several reasons. They were able to transform into a wheel-like configuration, allowing rapid movement and compact storage. When they encountered their targets, the bronzium-armored droids would unfold into a tripodal weapons platform, equipped with powerful, built-in twin blasters and often personal shield generators. These shield generators were somewhat powerful, capable of deflecting or absorbing any manner of blaster weaponry up to a light artillery bolt, as well as lightsaber blades and physical attacks. Additionally, the effectiveness of these droids was bolstered by the lack of true photoreceptors; instead, droidekas utilized non-visual composite radiation sensors, less likely to be distracted by mere light-based trickery.
In Star Wars: Battlefront and Star Wars: Battlefront II the droideka is one of the CIS units. It carries the normal repeating blasters and shield generator of its signature make and can be deployed into ball mode to roll and travel faster, and (in Battlefront II) the droideka can jump. In Battlefront I, the droideka can not shoot you if you are at point blank range in-between its blasters on either side of its body.
In Star Wars: Republic Commando, the droideka appears at least once on every mission, to the annoyance of the player. The droid is exceptionally strong and its repeating blasters can be devastating. The easiest way to kill these pests is to run up to it and stab it with your vibroblade, as the design of the droid does not allow the blasters to swivel inward to shoot a target that is close to it.
The Droideka Mark II soon became part of Tyber Zann's faction fighting in the Galactic Civil War, it featured several improvements incuding miniature Ion Cannons, allowing the droid to defeat many light vehicles with ease.