"Crab droids have a subpar targeting percentage, but deliver a profit of forty-eight-thousand credits per unit. They might not win the war, but they could save the Techno Union's fiscal quarter."
LM-432 crab droids were battle droids used by the Confederacy of Independent Systems during the Clone Wars. They were nicknamed "muckrackers" because of their extensive use in marshy terrain. Their name was derived from their six-legged scuttling movement and organic appearance.
Ranging from three to twenty feet tall, the crab droid could use its legs to attack infantry in its way. As well as their powerful pincer legs, LM-432 crab droids were armed with twin blasters located on the bottom of the droid's body. These blasters were capable of rapid fire and a powerful double blast. They were also equipped with a vacuum pump system integrated into their forward pincers, which could suck up and then spit out mud to either clear space for Separatist forces or obscure the visual sensors of enemy forces. This earned them the nickname of "muckracker". Crab droids also used their front two pincers to whack opponents out of the way or to crush them with their ends. The crab droid was also equipped with three glowing photoreceptor eyes and communication/sensor antennae- making it seem like it was a living creature rather than a machine- a feature many of the Separatist's droids included.
LM-432 units were protected by armorplast-shielding that could deflect blaster shots. The largest legs of an LM-432 unit were tipped with heavy duranium stabilizers that could secure perches on even bedrock. Smaller LM-432s were unable to rid themselves of opponents who got on top of them- veteran clones knew to avoid their cannons by leaping on top of them. When in pursuit of an enemy it could move very fast in short bursts to overtake it, and in this way run over their target.
Crab droids were first deployed in conflicts on marshy worlds, but their ability to cross difficult terrain and even scale jagged surfaces led to their usage elsewhere, such as at the Battle of Utapau.
Other variants of the LM-432 crab droid included tiny models for espionage and giant versions that served as mobile armor, which were capable of taking on Jedi. One rare variant was equipped with Gunganbubble wort projectors that could imprison their targets in force fields.
They were also heavily used as security in the separatist prison, Citadel. Many were used because of the rough terrain, to capture the jedi who were escaping.
Decades later, crab droids left from the Clone Wars were still utilized by the Empire during the Galactic Civil War, being used as scouts and sentries. [source?]Mace Windu impales a four legged crab droid while riding its back