On Saturday, the 20th level party in my campaign attacked a Cult of the Dragon outpost in a huge
river cave. The main players (in addition to the cultist riffraff) were an archmage (with a much-improved spell list), a spellcasting adult red dragon, an adult black dragon, and a dragonrider who was essentially an up-ranked champion with a magic lance that had a nasty stun effect. They'd had previous run-ins and the bad guys were scrying on the PCs (and vice versa).
The wizard had
true polymorphed mounts for the PCs, so the battlemaster was mounted on a wyvern, the warlock/battlemaster on a young silver dragon, the rogue on a unicorn, the lore bard on a Pegasus. The life cleric was on a warhorse because being flashy wasn't his style. The party split up (oops), with three attacking from the south and three from the north.
The archmage cast
greater invisibility and flew close enough to
feeblemind the life cleric. Failed Int save. Inspiration. Failed again. Another player donated inspiration. Failed again. Revenge of the dump stat. Life cleric has Int 1 and can't cast spells.
Red dragon casts
greater invisibility and quickly downs the battlemaster and his wyvern. The black and dragonrider stunlock and kill the young silver; the warlock/battlemaster nearly dies but manages to misty escape out of immediate danger with a few HPs left. The bad guys are essentially unharmed at this point.
The wizard then
true polymorphs the
feebleminded dwarf cleric into an ancient white dragon. The rogue jumps on the dragon's back and they go take on the red. Meanwhile, with illusionist ability,
mirror image, and
shield, the gnome wizard has to tank the black dragon and dragonrider for a few rounds all while maintaining concentration on the
true polymorph. The red dragon's breath recharges and it tries to use
misty step to get away from the ancient white and finish off the bard and gnome, but the warlock/battlemaster counterspells. The red decides to eat AoOs from the white and the rogue to kill two vulnerable characters anyway, but the rogue has Sentinel and it can't get away. The rogue finishes it off with a rapier in the eye.
Then the gnome wizard finally goes down under the onslaught of the black dragon, dragonrider and archmage. And when he goes down, the
true polymorph goes down, and the once-more
feebleminded dwarf and the rogue fall eighty feet. Now the dwarf decides to ask about divine intervention... I rule he's a drooling idiot, but his faith is still strong. His prayer doesn't amount to much more than "Gaaaaah!" The effect I choose is a lowly
greater restoration to remove the
feeblemind. Now the 20th level life cleric is back in the game and the party is easily able to win the battle.
It was cool.