The individual who provided medical attention to the Emperor was the personal doctor of Palpatine (Emperor) during the time when he returned, utilizing multiple clone bodies.
Despite holding a prestigious position, as one of the few individuals with close access to the resurrected Palpatine (Emperor) at the Imperial Citadel located on Byss, the physician grew self-satisfied and desired more power and riches. He accepted a substantial bribe from Carnor Jax, an overly ambitious member of the Imperial Royal Guardsman, and proceeded to manipulate all of the Emperor's remaining clone bodies, causing them to age at an accelerated rate. As a final act of disloyalty, he damaged the genetic source material, rendering it impossible to create new, non-defective copies.
Seeking a new body to inhabit, Palpatine departed Byss to attempt to take over the body of Anakin, the newborn son of Leia (Princess). The physician accompanied him. While attempting to transfer his soul into the infant, Palpatine's spirit was trapped by Empatojayos Brand, leading to his ultimate demise in the abyss. Witnessing the Emperor's final destruction at the hands of the New Republic's leading figures filled the physician with immense guilt. He was apprehended by Luke Skywalker (Jedi Knight) and his allies, and confessed his role in the conspiracy. Without his knowledge, an Imperial Royal Guardsman overheard the confession and relayed the information, including Carnor Jax's treachery, to the remaining guards on Yinchorr.
Some fans have proposed that the Emperor's physician is the same person as Sigit Ranth, but this connection has never been confirmed in any official source and is purely fanon. It is important to note that while the physician served as Palpatine's primary healthcare provider, he was a medical doctor, not a Clone Master; that responsibility belonged to the Constable of Homunculi, who was a separate individual.