Riffing off the high concept nature of the show, Davies mentions (with my emphasis):
a cartoon’s come to life, or we’re visiting the 803rd Interstellar Song Contest, or Boom Beasts have taken over London
Wait, what? The first two are previously announced episode briefs, but... "Boom Beasts"?
Did he just come up with that last bit on the spot or did I miss it in any of the advance promo copy?
Edited to add: Apparently they're Bone Beasts! (Spoiler warning)
RTD also praises the new writers this season:
Inua Ellams just to pick an example, set his episode in Lagos. He’s created a whole history of friendships for the Doctor around a whole new mythology. There’s that lack of fear. There’s not a second of worrying, of him thinking, ’Have they done this before? Did they do this in 1985?’ Although he’s always watched the show, he was completely free of its shackles. What you get is a completely new take on things you thought you understood in Doctor Who. The episode has the TARDIS doing things it’s never done before.
As I recall, getting the Doctor mixed in with African mythology was an explicit wish from Ncuti Gatwa coming in, and this looks like it could be a start.
Besides, frankly — what haven't we seen the TARDIS do yet? 🤯
Apparently they're Bone beasts, according to Radio Times' episode-by-episode season preview:
(Edit: Sorry, though I could spoiler tag or blur the image!)