Skyscraper
Adventurer
I have no experience playing those levels, but I admit that this list is a bit unsettling.
This is one of the reasons I worry about high-level play for casters. Going from ~five 8-9th level spells/day in prev editions to a single spell/day is really gonna suck when legendary monsters can 'choose' to save 3x/day and beyond that everything has some form of energy and magic resistance. I don't know for a fact, just a bit leery.
Except odds-are there's a good chance you could have 2 to 4 characters in the party with 8th and 9th level spells. So that's 4 to 8 spells of those levels that the legendary monsters will have to try and save their way through. Even with 3 insta-saves... there's still plenty of magic they're going to be nailed with.
5+ high level spells per character would means upwards of 10 to 20 of those spells per day at a party's disposal (or to be really truthful... 20 to 40 spells per day when you account for the 8 hour rest in the middle of the afternoon the groups would inevitably take). That's exactly where the idea of high-level casting being unbalanced in previous editions came from.
Well one thing is you gotta let this high level creatures survive on their own. Relying on liars and minions to stop Big Spells makes their CR false since they suck alone outside their lair.
Except odds-are there's a good chance you could have 2 to 4 characters in the party with 8th and 9th level spells. So that's 4 to 8 spells of those levels that the legendary monsters will have to try and save their way through. Even with 3 insta-saves... there's still plenty of magic they're going to be nailed with.
Then their CR is already false because they'd suck if the party had another Ranger instead of a neutered Wizard, so never come up against the resistance.
So from the looks of things, my wizard (assuming he reaches high levels) will be relying mostly on passive buffs rather than direct effects, since magic will prove to be rather ineffective against the majority of high end monsters...
Yay.