Into the Tier 3 Frontier

My Ravnica campaign has made it to tier 3, and that means players are level 11. Several players decided to try out alts, so I made a less plot-intensive adventure before they pick their new headquarters (and prepare to clear out monsters from their choice) in which they traveled to a remote district to deal with what turned out to be an adult white dragon who had frozen the whole place.

It's the first time I've run a legendary dragon, and I'll be honest, kind of shocked at how quickly they took it down. Four characters, three of whom literally had no magic items (except some healing potions they bought.) But there was an Open Fist Monk, a Chronurgist Wizard, an Undead Warlock, and the veteran character, an Ancestral Guardian Barbarian.

Even between only four characters (though the Warlock did use the Conjure Undead Spirit spell, which is freaking powerful) the party took the dragon down before he got a second turn - the dragon only got two legendary tail swipes, two legendary wing buffets, and a single frost breath before he was taken down.

A group of four level 11 characters is supposed to be balanced for a CR 13 legendary monster, but this felt like a cakewalk (though the Wizard was down to about 5 health after the breath attack.)

So as I see it, I think I either need to build in environmental disadvantages or I really need to make sure that any big encounter (even if it's not a plot-focused "boss") has the legendary creature's health maximized.

I do think that a lot of the difficulty scaling for encounters is based on an assumption of a lot more combat per day - more of a dungeon crawl experience. If you're having six fights before a long rest, with maybe time for one short rest in the middle, even fights that go quickly will deplete resources and health.

Something to think about.

But yeah, an adult white dragon only has 200 health on average. And when you have players at level 11, it's not terribly unusual for them to do over 25 damage in a round, so between 4 players, it'll only take them two rounds to kill it.