Voadam
Legend
Otto's Irresistible Dance for example.
Forcecage + Dimensional Lock also works, but requires some serious tools to make that happen in one round.
Swift +10 to Penetration for 1rd/lvl against the target.
Otto's Irresistible Dance for example.
Bye
Thanee
Oops, I was screwing up in my head what level spells you can cast at 15th and thinking it was only 7th.

That is a good no save 8th level core spell that will take the BBEG's actions away for 1d4+1 rounds.
It would require the noncore assay resistance to to punch through the SR though if it is going to work reliably.
It is a touch spell so he must go in close or use a spectral hand.
The quickened truestrike could not be done the same round as the swift assay resistance so to do so he'd need to have at least a round buildup.
It would work though if you have the assay going.