Makuta

The Makuta were an incredibly rare, shadowy, non-biological species associated with the dark side of the force. They were originally created by the celestials long before that race came across the galaxy, and served them for hundreds of millenia before finally rebelling against them in 49000 BBY, and killing the Mata Nui, ruler of the Celestials. This coincided with the rebellion of the human slaves and destruction of a massive portion of the celestial fleet by the force sensitive planet Vitea. After 10 years of war, the celestials were forced from the galaxy and the Makuta faced near total destruction.

The shadowy beings would continue to exist, however, planting their evil into the bloodline of the sith  of korriban, who would later gain members of many other species for their cause.

The Makuta are also credited with poisoning such worlds as Tund, Dromund Kaas, Ambria and Nemtox with the dark side of the force. The Makuta were also, for a long time, in possession of the Eliminator, a titanic sith weapon they eventually passed down to the tribal sith on korriban.

Biology and Appearance
The Makuta were created artificially by the celestials, and they function by absorbing energy from the dark side of the force. They have no real bodies, they consist of force energy inhabiting an armoured shell. This made them extremely hard to kill, and they were often able to rebound from defeat.

Makuta were originally designed to be 2 metres tall, but after the defeat of the celestials the size could vary greatly, as the Makuta could easily augment their shells or move into new ones. Makuta Teridax often stood 4 metres tall, for instance. A makuta could also decrease it's size to disguise itself. Makuta Vamprah spent 100 years disquised as the protocol droid L-3PU.

Due to their lack of a biological body, Makuta did not age and were supposedly immortal, able to live for tens of millenia. Eventually, their bond with the dark side would decay, however, and they would cease to exist. Makuta Teridax was 700'000 years old by the time of his death.