The Master dreams in Gallifreyan now. Perhaps he did so even before the Doctor's little confession. But he notices it, now. The sound of Gallifreyan catches the attention, like footsteps in an empty room.
He'll never speak it again except in dreams, or to the Doctor. All its ways of distinguishing time (thirty-eight verb tenses, pronouns for past and future incarnations) are useless in this new universe of linear beings. Not even Lucy, whose mind has opened to cold infinities, could ever really understand.
The language is the only loss he regrets. If someone's going to weep over the red grass, the inspirationally-named mountains, the Citadel and every pompous Time Lord inside, it'll have to be the Doctor.
He looks forward to watching it.
If only he'd thought to record that phone call. He spoke in Gallifreyan, naturally, and across the miles he felt the Doctor shudder. Answering in Gallifreyan, the Doctor called him "Master."
Words are forms. Thoughts flow into them and take their shape. He is Master now.
He's Gallifrey now, to the self-orphaned Doctor, the lonely parricide.
There's no word in Gallifreyan for "homesick." How could a race that's calcified by rules, as immobile as fossils, imagine such a thing? No more than they could imagine their planet scuffed out, their language uprooted. A souvenir carried away in the baggage of Gallifrey's two last and most undutiful children.
He doubts the Doctor thought of Gallifrey as home before he burned it. All his fondness is retrospective.
There should be a word for it: the love you feel for what you destroy.
Maybe they'll make one, he and the Doctor. A secret word, theirs alone, in Gallifreyan.
It'll come in handy.