For those that haven't faced this dungeon yet, you can only use the 4 elves. I find the elves generally useless and hadn't bothered to level them, but for this challenge I did, and pulled superior and elite legendary 5 star runes from all my unused heroes to strengthen them.
Even so, I got through this using continue potions and friends, because my Elves are so abysmal they even at level 80 with superior and elite runes they still died like flies. Defense of 8-9k and health of 12k makes no difference. Only Daeris has any form of non rune-based healing, and only Indigo has any team synergy (boosting energy on crits). Vampire runes made no difference as they don't activate reliably enough.
This is the highest level dungeon that forces you to use a select 4 heroes family, and they have next-to-no team synergy as a family. The only thing they are all good at, fighting flying enemies, makes no difference as none of the enemies in this dungeon are flying. The Yasmin clones can mass resurrect, so you have to target then first and hope the remaining heroes don't do too much damage while you do.
Is it just a matter of slapping on some healing runes, reviving when necessary with potions, and using friends to do all the hard work, or is there some way to use the Elves themselves to help, rather than just have them be passengers?
In comparison my Dwarves breezed through Chapter 21 Garden of Evil (B) first try on autorun, to get the Birthday quest title and gems.