relationships/people the master ~consorts with.
andsosyourdad
Not that he would admit to it, but: the Master's big O. This is his tenth, and he harasses him a lot. They bicker, screw, follow the other one around, and generally avoid being in any semblance of a relationship. Ten sculpts statues in his likeness, and the Master blows up his favorite fruit. They are both as crazy (and stupid) as the other, and the Master isn't alright with the knowledge that he isn't going to ever find a Ten quite like this one. The Master can insult him all he likes: you cannot.
oneshotsaxon
His ex-wife (though you'll find he still refers to her as his wife), and murderer, she also managed to finagle her way into his life as his best friend. There is not a single woman in his universe or any other that understands him and puts up with him as well as Lucy does, and their evenings are usually spent sitting in front of the TV with chinese take-out watching The O.C. She is also the only person he'll admit to loving, and he has copious amounts of respect for her.
presidentromana
Yet another of the Master's love/hate relationships (he loves it, she hates it), Romana is someone he knows is attracted to him, and he dedicates a lot of his time to either harassing her or trying to get into her pants. He plays at having little to no respect for her, and that's just fine with him.
victormakesart
He has little patience with Victor, though he thinks she's above average intelligence (as far as stunted apes go). Generally, Victor is the one he goes to when he finds himself in a perpetual state of boredom. He's not above hurting her if he wants to, and he enjoys the reaction she has when he does. Her low self-esteem constantly grates on his nerves but he likes how uncomfortable Victor gets when he throws a compliment her way.
apportare
They talk, basically. Nathanial is, generally, the person he talks to the most as far as the Room is concerned. There isn't any particular reason why, but with the lack of interesting conversations available to him, the Master finds the other man's presence tolerable enough.
ginger_romana
Another Romana he likes to harass. He knows she's afraid of dying, afraid of the end of the war and the end of Gallifrey itself, and he has an absolute blast throwing that in her face. She is, currently, his favorite person to taunt, and he's liable to begin stalking her soon.
vworp_vworp
The Doctor's TARDIS. As a human. Oh, and he's pretty certain she might be dying. Interacting with her is both entertaining and, frankly, unusual. He's offered to help her, which isn't a guarantee that he will - he knows there are a surplus of opportunities here that could benefit him in the long run.
In progress.