Empowered Spell before and after Spell Bombardment

Question

The Empowered Spell metamagic option says:

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell.

The Wild Magic sorcerer's 18th-level feature, Spell Bombardment, says (PHB, p. 103):

Beginning at 18th level, the harmful energy of your spells intensifies. When you roll damage for a spell and roll the highest number possible on any of the dice, choose one of those dice, roll it again and add that roll to the damage. You can use the feature only once per turn.

Suppose we have an 18th-level wild magic sorcerer, and suppose that he has a Charisma modifier of at least +2. He casts fire bolt, hits, and rolls a 1 on the d10 for damage (let's ignore the rest of the dice). Expending a single sorcery point, he empowers the spell and rerolls the die. This time, it's a 10. Our sorcerer now uses Spell Bombardment to get an extra d10 of damage. This one is a 1 as well. Does the Empower Spell from before allow him to reroll this second die as well?

Answer 1

Empowered Spell is a one-time choice.

The Empowered Spell metamagic option is a one-time choice. When you roll damage for a spell, you can choose to spend a sorcery point to reroll a number of the resulting damage dice equal to your Charisma mod. It doesn't matter whether additional damage is added by other features after the fact; you choose the dice to reroll when you roll the initial damage of the spell. There are no "carryover" effects to additional damage dice.

Thus, the logical move is to use Empowered Spell after all damage dice for that spell have been rolled. You can't do the following:

1. Roll the initial damage dice, and fail to get any max-value damage dice
2. Reroll using Empowered Spell to try and get a max-value damage die
3. Roll an extra damage die from Spell Bombardment after you do get a max-value regular damage die
4. Somehow get a reroll of your additional damage die

Specifically, steps 1-3 are allowed, if the events occur that way. It's step 4 that doesn't work; even if everything else goes as described, you can't split the usage of Empowered Spell into multiple steps.

In the same way, if you have a Charisma mod of 5, you can't reroll a single damage die, and then keep rerolling the same die 4 more times if you keep getting a low result. Even if the Empowered Spell description didn't rule it out explicitly, all of the rerolls happen at the same time. You can't choose to delay some of them.

Answer 2

This doesn't work because Empowered Spell's rerolls all happen simultaneously

I believe that Empowered Spell only lets you reroll damage dice that you just rolled. The feature states:

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one) [...]

I read this as only allowing you to reroll damage dice that were rolled when you used Empowered Spell. Otherwise you could use it on a spell like booming blade, rerolling dice from the initial attack as well as the damage that occurs when the enemy moves with a single use of Empowered Spell.

This means that if you use Empowered Spell and it ends up allowing Spell Bombardment to proc, you have already used up Empowered Spell and any remaining rerolls can't apply to future dice.

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That said, allowing this as a houserule seems quite reasonable. It's a small increase in damage and Wild Magic Sorcerer isn't a particularly strong subclass (or even class).

Answer 3

Yes

“Rolling damage” means rolling all the dice. The extra dice from spell bombardment are just “dice” and can be rerolled with empowered spell. Similarly, the rerolls from empowered spell are just dice and subject to spell bombardment.

Answer 4

A non-rules based option: It's fine to let it work.

The Empowered Spell metamagic option is weak, especially when compared to something like Quickened Spell, and it averages out at something like 2-3 additional points of damage. There may be little in the way of rules-based support for this, but on the scales of balance I don't see a problem in allowing it. Spending a sorcery point, even if you get 20 damage from it, is a significant cost, and the same point could have just cast the cantrip again with Quickened Spell, so it works out to be equal.