"The Apprentice" is a short comic story that can be found inside of Star Wars Tales 17 and also as part of the collection in Star Wars Tales Volume 5.
Finn, a Sith Lord, and his student are located on a remote planet where they detonated a bomb inside a structure. While returning to their spacecraft, they encounter Lod, a Toydarian who presents Finn with Marka, his blue-haired Human slave girl. When Marka declines to display her teeth to Finn, Lod strikes her, prompting the apprentice to shout at him to cease. Lod suggests to Finn that he should monitor his slave more carefully, but the apprentice retorts that he is not a slave, and then uses his lightsaber to kill Lod.
Finn rebukes his apprentice for displaying compassion, which he sees as a Jedi characteristic. Marka then requests to accompany them, employing a mind trick on the apprentice. Finn declines, stating he doesn't require a slave since he already has an apprentice. The two Sith then depart, making their way back to their vessel. Finn instructs the apprentice to handle Marka while he goes to the roof of the building where their landing platform is. Shortly after, the apprentice comes back with Marka, admitting his inability to kill her. Finn reiterates to Marka that he already possesses an apprentice.
Marka then grabs the apprentice's lightsaber and shoves him from the top of the building, resulting in his demise. Finn simply asks Marka if she intends to join them or not.