Oh, one more fun thing you can use exactly once. A future copy of a PC arrives and helps them. (for extra fun, a future copy of a PC broken by mind flayers arrives and hinders them, possibly via deception; that should happen 2nd mayhap).
You want this to happen once, because it foreshadows the PCs themselves doing it at the end of the plot. And only once, because it sort of steals player agency. That PC lived through a variant of the campaign where the PCs lost (or didn't win good enough), and has come back to boost the PCs somehow. They should have a very limited lifespan for some reason, so they don't help too much, but they should provide heavy spoilers for the next thing the PCs do.
Also, the mind flayers should taunt the PCs with "we are inevidible" when they are losing. Especially if there is a armor artificer.
Also, enslaved future copies of NPCs! Especially long lived ones, like liches or elves.
Oh, an enslaved god (from the future), driven mad, and rode by a huge intellect devourer, visible through a hole in their head. Maybe with a bio-cybernetic limb. Possibly one a PC follows. Reduced from godhood, but still a power to be reconed with.
You want this to happen once, because it foreshadows the PCs themselves doing it at the end of the plot. And only once, because it sort of steals player agency. That PC lived through a variant of the campaign where the PCs lost (or didn't win good enough), and has come back to boost the PCs somehow. They should have a very limited lifespan for some reason, so they don't help too much, but they should provide heavy spoilers for the next thing the PCs do.
Also, the mind flayers should taunt the PCs with "we are inevidible" when they are losing. Especially if there is a armor artificer.
Also, enslaved future copies of NPCs! Especially long lived ones, like liches or elves.
Oh, an enslaved god (from the future), driven mad, and rode by a huge intellect devourer, visible through a hole in their head. Maybe with a bio-cybernetic limb. Possibly one a PC follows. Reduced from godhood, but still a power to be reconed with.