Dungeon Ideas: Banshees, Elves, Vampires & Changelings!

Adventure Context: Cordelia the Banshee has stolen her child's heart (literally). This heart comes from a changeling (one of the players), and is infused with magic that allows wondrous feats to be performed. Making her lair within an ancient temple once used by elves to turn themselves into vampires, Cordelia hopes to use the heart to 'bring an end to death'.

If anyone has any ideas for fun/thematic encounters, then please throw them at me!