None at all.
That's the Master in disguise as "Kalid", though I personally think the Doctor's on to him by now. The Master's pretending, for poorly explained reasons, to be a sorceror with an Incredibly Dodgy Accent. He's getting off on talking about how with the power of the Doctor's TARDIS he can take over the universe. Must be Tuesday.
The Doctor says "I've always found domination such an unattractive prospect." Look at him biting his finger as he admits he prefers to be a sub! Look at the way the Master turns round to look at him!
"Shall I be forced to compel you, Doctor?"
The Doctor gets a bit bratty, claiming the Master'll never get what he wants. Yeah right.
Nyssa looks unhappy that Tegan's hand isn't further down.
Nyssa is very keen that they go ahead into the caves (and we all know what caves represent). "We must find the centre. Trust me."
It's hard to see on the cap, but the secret entrance has just opened, and I think we all know what that means. "We must continue," Nyssa insists.
The incredibly gay flight crew + Professor thingy in hi-tech bondage.
And here is the Doctor knowing the Master has him over a barrel because he's got captured innocents. (This would probably work better as a video clip, really; the way he's breathing in and out is very subby.)
Right, here we go with the real subtextual stuff. Nyssa and Tegan have to confront and deny the reality of various symbols of The Issues Around Their Relationship. The first is Adric, who represents Boys Who Fancy Them, or something. Tegan is actually the one who says "Come on" here after Nyssa convinces her.
And now we have the Melkur, who represents Nyssa's incredibly fucked up father issues.
And now a Terileptil, who obviously represents Teh Cock. "You're not real."
"Just help me!" Nyssa yells as they rub the bud-like thing, breathing heavily and grunting. She's very close
And this is the Master with his lippy on, just 'cos.
All dialogue quoted exactly, honest!
You know, I always used to think of Tegan as the sexual aggressor in that relationship. No longer, Internetz peeps, no longer.