Tempest domain builds come online faster than ever.
Yes, this is yet another evocation adept post. I wonder how many of these we need before people accept that this is a problem.
So AOE nova is pretty rare, but tempest domain has always been a fun pick to try to optimize around for AOE nova builds.
Back in 5e, we had builds that dipped into tempest domain for 2 levels but were mostly sorcerer. These builds transmuted fireballs from fire damage to thunder damage and maximized a 4th level fireball for 54 damage at level 7(sorcerer 5/cleric 2). These builds could do this once per short rest and couldnt really afford to take more cleric levels because they were charisma based(so they wanted more sorcerer levels) since there were no good ways of getting a wis based fireball(for that build). If you wanted to go cleric 6/sorcerer 5, you would become a one trick pony that did very little other than to go nova in turn 1.
Fast forward to early days of 5.5e, we had cleric subs at level 3, so this build got online even later, and level 7 was already late enough. Then we saw a new build, tempest 3/sea druid 5. This also came online at level 8 but it had a wisdom based lightning bolt. It was also fully wisdom based so as you level up either class, you would get spells like spirit guradians and conjure woodland beings which upcast fairly well too. This build could do 54 damage at level 8 with a 4th level fireball but it had an additional use of channel divinity thanks to the 5.5e cleric buffs and it could level cleric to level 6 to get even more channel divinities so you could go nova every combat. This build had the weakness of relying on the significantly worse AOE of lightning bolt and the more commonly resisted lightning damage. You also had only 2 4th level slots at level 8 as you cant create more like a sorcerer could.
And now in 2026, everbody has fireball. You get fireball, and I get fireball, and everybody gets fireball. Its like the old darkvision meme. So now, a level 4 tempest cleric/level 2 sorcerer can take the evocation adept feat(which gets them to 18 wisdom), and transmute their fireballs to thunder damage. Yes, in case you didnt know, multiclassed casters can use evocation adept to cast the spells that they have the slots for, even if they cant normally prepeare spells of that level. This build can add 2d8 hit die to the damage of their thunderballs(which also get maximized with the rest of the dice) and deal 64 damage at level 6. This character can do this 3 times with a single short rest, only the final one will be 60 damage as you will be left with sorcerer hit dice.
This build is fully wisdom based, so you can comfortably level up cleric to get more d8 hit dice, more wisdom based high level spells, and more channel divinity uses. It doesnt have the weaknesses of either the sea druid or the old sorcerer build. You get wall of force at level 9, which neither used to get. From a standard optimization lens, you get armor from cleric and the shield and absorb elements spells from the sorcerer levels. At some point you can take the 3rd sorcerer level for a usefull subclass like wild magic and also get second level spells like misty step, blur, mirror image, etc. that are not reliant on charisma and clerics lack.
Im not gonna provide a full build, this is the core and you can take it various ways from here. The 64 damage 6th level is obviously a very high peak, the damage gets comparatively less impressive as you level up. Even then the build stays solid because evocation adept allows you not to be one dimensional. Let me know what you think.