A friend recently pointed out to me that by using a Tempest Domain cleric's Channel Divinity: Destructive Wrath and the Order of Scribes wizard's spell damage-changing feature, you can do a maximized fireball.
That got me thinking, and I dreamed up an even more powerful combo. Enter Vihaan Stormbringer, 2nd-level Tempest Domain cleric and 17th-level Order of Scribes wizard. Vihaan can use Awakened Spellbook to cast a Meteor Swarm that does lightning damage instead of fire and bludgeoning damage, and then maximize that lightning damage with Destructive Wrath. This insane combo will do 240 damage every time (with a Dexterity save for half), and this is an area spell that has an extremely large range! Is there anything in the rules to stop me from using this incredible combo?
Best Answer
This sorta works
In the Awakened Spellbook feature description, it states:
But meteor swarm has two damage types; fire and bludgeoning. As such, in a strict reading of the the feature, it doesn't look like it is built to change both. It is written assuming there is only one damage type per spell, which is true about 99% of the time.
You would have to talk to your DM to see whether they will allow only one damage type to be switched, or both, or neither. As a DM, I would allow the character to switch one, but that's just an opinion.
You have another problem
Awakened Spellbook continues:
You need to have a second 9th-level spell that causes lightning / thunder damage. It has been suggested that prismatic wall would fit the bill. This would be another DM call as the wall doesn't directly do lightning damage. It has the potential to do so, but only if someone enters the yellow layer, which requires crossing the red and orange layers first. This is similar to chaos bolt, which could do lightning damage, but doesn't necessarily. However a chromatic orb would be fine as the caster can declare the damage type at casting.
Also, prismatic wall is both helping you and hurting you. It has the potential to be a spell that does lightning damage, but it also has the problem of allowing the Destructive Wrath to affect multiple damage types. The wall has five different damage types. What would happen if the caster converted them all to lightning/thunder? That's a lot of max damage.
So in the end, it's really up to your DM whether they'll allow all of this to happen. And if this is for a one-off where you're automatically 19th level (17 wizard/2 cleric) to cast a 9th level spell, then see what happens. But if this is for a build where you're working up to that point, it seems like a lot of work for a one-time payoff.
Alternately, don't be a wizard
If this is a build where you're going to be spending effort to level up to reach this "capstone" of destruction, then don't be a wizard.
Take Sorcerer levels instead, any subclass; they get a metamagic feature called Transmuted spell:
This means you can swap any fire damage spell for lightning or thunder, regardless of level and if you have a matching spell.
No, you can't swap out the bludgeoning damage in meteor swarm, but you'll have the same "swap to lightning" effect with any other spell along the way to that point.