Em-One, also known as M-1, was a mouse droid of a scarlet hue. This particular droid formerly belonged to Komat, an ex-member of the Acolytes of the Beyond who was once a member of the Imperial forces. When she was living in exile on the planet Polaar, she used M-1 as a warning system because of the distronic radiation poisoning present on Polaar. During 21 ABY, upon the arrival of Lando Calrissian and Luke Skywalker at Komat's residence, M-1 was the initial entity to welcome them, though it did so with beeping sounds, indicating that the two were vulnerable and experiencing the initial effects of distronic radiation poisoning. Subsequently, following a skirmish involving battle droids dispatched by Kiza with the intention of recovering kyber crystals that Skywalker had located, M-1 employed an electric saw to detach the head of the leading droid. It then dragged the head to Komat, Calrissian, and Skywalker, allowing them to examine it.