R2 Grievous

Made a four arm service droid. You might be lucky enough to hire him as a bounter hunter

Story:
An R2 unit from the clone wars era who has served under Commander Grievous loyally without question and has witnessed every battle besides him with every record. However after the battle between Master Obi-Wan Kenobi and Grievous the death of his master has suddenly granted the servant droid the feeling of “hate” and began to suddenly wield the “force”. Driven by vengeance the servant droid began to gather parts from droids and began to them as his own to exact revenge against the Jedi Order and the Republic.
With another head on top, it serves him to have more eye but also to channel more processing power within his inner systems. It also serves him with more arms to wield his former masters lightsabers to defend himself but to also replicate the memory of his fallen Master.
The tank tracks serve as his means of overcoming any terrain, possibly stealing these from a treadwell droid and ref