MD-5, also known as Emdee Five, functioned as a medical droid—specifically an MD-5 medical droid—for Trioculus, the self-proclaimed Galactic Emperor, during the year 5 ABY.
The droid MD-5 was always with Trioculus at various events, including the public speech given by Trioculus at Kessendra Stadium located on Kessel, and aboard the whaladon-hunting submarine commanded by Captain Dunwell. Trioculus and MD-5 had a strong connection, much like the bond that existed between Luke Skywalker and his droid companions, C-3PO and R2-D2.
On one occasion, MD-5 implanted cybernetic enhancements into Trioculus's fingers, which gave him the ability to mimic the effects of Force lightning. Later, MD-5 also placed small devices into the fingertips of Darth Vader's glove, which allowed the wearer to imitate the power of Force choking.