I ♥ Nyssa/Tegan so hard. They are one of my favourite ships for angst purposes. There's so much fairly horrible backstory for both of them. A lot of it revolves around the Master, what with him killing Aunt Vanessa and stealing Nyssa's dad's body before destroying her planet, but there's also Tegan's experience with the Mara and Adric's death (just because the fans and apparently the cast were glad to see him go doesn't mean the characters were). Here is everybody dealing with Adric's death:
Now admittedly, all that angsty backstory stuff's hopelessly underexplored in canon (though not quite as much as is sometimes made out -- in the two-episodes-a-week mode things did get a bit more soap-operatic in the plotlines-continue-and-have-consequences sense; the stories blend into one another much more than in most other non-b/w eras). But at the same time, that lack of exploration contributes to one of the things I like about them, that they don't wallow in their angst when there's universe-saving to be done, they get on with confronting the bullshit the universe has to offer them with fierce faces like these:
(Incidentally, everyone mocks the "uniforms" thing in S19, and it does raise unfortunate questions about whether temporal grace applies to your armpits as well, but secretly I like the fact that their outfits are quite colour-coordinated and batshipperly see it as Proof.)
They are even fierce when youthified by random technobabble in Mawdryn:
Being Five era companions, they spend quite a bit of time in the TARDIS
And here is a nice publicity shot from the beginning of Season 20:
It is Nyssa/Tegan's ending that is the angstiest part of all for me, because Nyssa gets the Good Ending and Does The Right Thing, but that just makes it more heartbreaking because it is all noble-sacrifice-y. Here are some caps from the goodbye scene from Terminus:
"Don't leave me!"
"I kinda have to, out of valuing our personal happiness lower than the wellbeing of large numbers of people in the bigger picture."
(Y HALO THAR, Rusty characters who could stand to learn a thing or two in this regard. And, yes, I do really love the ending of Casablanca, what of it?)
I have been writing fix it fic of this in my head since forever, and I did finally make a version work enough to be let out to play for last year's dw_femslash.
(I cannot find a picture of Tegan's cry face, but it is epic; if I can get my DVD drive to play ball, expect lots of picspammage when the Black Guardian trilogy arrives on DVD)
You really have seen all these before, but they're so cute, so have them again:
These ones have clearly been scanned in from a newspaper and are hopelessly low quality, but I couldn't find better alternatives and they're still very cute:
These pictures by themselves are enough to make me ship them against all the canon logic of "Turlough's still quite evil at this point in canon, has barely interacted with Nyssa at all, and then she leaves". In fact, those cogs you can hear whirring are me working out rubbish AU scenarios where she stays and it's all a big glorious OT3. Ahem.
(all nabbed from shillpages and THT, obviously)