Is there anything to stop me from using this OP combo of Destructive Wrath and Meteor Swarm to do 120 or 240 damage?

Question

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?

Answer 1

This sorta works

In the feature description, it states:

you can temporarily replace its damage type with a type that appears in another spell in your spellbook,

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 to assuming their 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 if they will allow only one 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

The latter spell must be of the same level as the spell slot you expend.

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, but only if someone crosses the red and orange layers first. Similar to chaos bolt doing lightning damage. 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 of being a spell that can do lightning damage, but it also shows the problem of allowing the Destructive Wrath to effect multiple damage types. The wall has five different damage type. 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 if 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. 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:

When you cast a spell that deals a type of damage from the following list, you can spend 1 sorcery point to change that damage type to one of the other listed types: acid, cold, fire, lightning, poison, thunder.

This means you can swap any fire damage spell for lightning or thunder, regardless of level and if you have a matching spell.

Yes, you can't swap out the bludgeoning damage in meteor swarm, but you'll have the same "swap to lightning" effect with any spell along the way.

Answer 2

Summary

Talk to your DM, there is a lot of interpretation going on. Let them think about it ahead of this being thrown down on the table. Think cooperative, not adversarial.

Long Form Cited Response

Speak to your DM. I think of this as adversarial to 'surprise' your DM with this, if I had to make a ruling on the fly, I tend to shoot things down that I might see the reason behind when I have time to look at it. I don't like to stop play to read rules. This had me looking in 3 places of one source book, and a second source book. I would never take that time in session.

I think the biggest problem is your DM's interpretation of the Awakened Spellbook line

When you cast a wizard spell with a spell slot, you can temporarily replace its damage type with a type that appears in another spell in your spellbook, which magically alters the spell's formula for this casting only. The latter spell must be of the same level as the spell slot you expend. TCE, page 77

Obviously, we assume you have another lightning spell in your WIZARD spell book. But crucially, I think the DM has to rule on:

you can temporarily replace its damage type

Meteor Swarm does not do a single type of damage.

Blazing orbs of fire plummet to the ground at four different points you can see within range. Each creature in a 40-foot-radius sphere centered on each point you choose must make a Dexterity saving throw. The sphere spreads around corners. A creature takes 20d6 fire damage and 20d6 bludgeoning damage on a failed save, or half as much damage on a successful one. A creature in the area of more than one fiery burst is affected only once.

Your DM will need to decide if Meteor Swarm does a replaceable single type of damage or if both are converted.

20d6 fire damage and 20d6 bludgeoning damage

I would be tempted to tell my player that in a 1 shot, sure go ahead and abuse it. You've got 1 9th level spell, let it be epic. Were it a campaign and this was going to be months of play, I might leave it up to the table. Personally. I'm tempted to interpret this as you can replace the fire damage as lightning, the spell does fire damage.

Blazing orbs of fire plummet to the ground

To me, the Spell does Fire damage, you can convert that to lightning, the falling does the bludgeoning. But again, it's DM prerogative. I think it is important to talk to your DM. I know MY rulings get more favorable the more my players chat with me and TRUST that my aim is everyone's fun.

Reference

Destructive Wrath

When you roll lightning or thunder damage, you can use your Channel Divinity to deal maximum damage, instead of rolling. PHB, page 62

Answer 3

This does not work (or at least, it is your DM's call)

The Awakened Spellbook feature says:

When you cast a wizard spell with a spell slot, you can temporarily replace its damage type with a type that appears in another spell in your spellbook, which magically alters the spell’s formula for this casting only. The latter spell must be of the same level as the spell slot you expend.

The featured refers to a single damage type, not to damage types in plural. Meteor Swarm does not have a single damage type, it has two damage types, fire and bludgeoning. Hence, it is not a legal spell for the use of Awakened Spellbook feature. You need a spell that has a single damage type.

The two damage types in meteor swarm are not a new "combined" damage type either, there is no such thing in the game. The PHB defines Damage Type on page 196:

Different attacks, damaging spells, and other harmful effects deal different types of damage. Damage types have no rules of their own, but other rules, such as damage resistance, rely on the types. The damage types follow, with examples to help a DM assign a damage type to a new effect.

The introduction does not say "some damage types follow". It is "The damage types", all of them. Then the types follow, and there is nothing in that list that would be a "mixed" type, and no language about it, either.

It is well possible that the author of the Awakend Spellbook feature failed to think of spells that deal more than one damage type, but this question is about rules-as-written, not about intent:

"Is there anything in the rules to stop me from using this [...]?" (Emphasis in the original).

Yes there is. I don't know if it is intentional. But on a strict reading of the text as written, this won't work.

If you and your DM feel that the letter of the text is an error if read strictly, for meteor swarm, DM could allow you to bend the written rules a bit and replace one or both of the damage types with lightning damage in spite of the written text. Your wizard will need to know prismatic wall too, because he needs access to a level 9 wizard spell that has lightning damage appear in the spell, and that is (to my knowledge) the only one that does.