How does an Evocation wizard's Overchannel feature interact with the Chaos Bolt spell?

Question

With the release of Guildmaster's Guide to Ravnica, characters were given new background options. All of these options add spells to a character's spellcasting classes. One of these is the Izzet Engineer background, which allows for any spellcaster to learn and cast chaos bolt, among other spells.

The Izzet Engineer background's "Spell List" section says:

For you, the spells on the Izzet Guild Spells table are added to the spell list of your spellcasting class. (If you are a multiclass character with multiple spell lists, these spells are added to all of them.)

Spell Level - Spells
Cantrip: produce flame, shocking grasp
1st: chaos bolt, create or destroy water, unseen servant
[...]

The description of the chaos bolt spell says:

You hurl an undulating, warbling mass of chaotic energy at one creature in range. Make a ranged spell attack against the target. On a hit, the target takes 2d8 + 1d6 damage. Choose one of the d8s. The number rolled on that die determines the attack’s damage type, as shown below.

d8 - Damage Type
1: Acid
[...]
8: Thunder

If you roll the same number on both d8s, the chaotic energy leaps from the target to a different creature of your choice within 30 feet of it. Make a new attack roll against the new target, and make a new damage roll, which could cause the chaotic energy to leap again.

Combine this spell with the School of Evocation wizard's Overchannel feature:

Starting at 14th level, you can increase the power of your simpler spells. When you cast a wizard spell of 1st through 5th level that deals damage, you can deal maximum damage with that spell.

I found another question referencing wish-ing to chaos bolt. The answer references the fact that chaos bolt is not a wizard spell, and therefore the asker's desired outcome does not work. However, a key point of text from the Izzet Engineer (emphasis mine):

For you, the spells [...] are added to the spell list of your spellcasting class.

This means it is now possible for a 14th-level Izzet Engineer Evocation wizard to choose to maximize the damage of a casting of chaos bolt. What happens if they do so?

Does the spell continually leap to new targets until the caster chooses no target? Since the damage is maximized, is it dealing thunder damage each time?

Am I simply too excited about this possibility? Should the 2d8 should be rolled as normal to determine damage type and leap potential, but then the spell deals 22 damage (8+8+6) regardless of the roll result?

Answer 1

Overchannel replaces the damage of the spell, not any other mechanics

The only thing that changes when you overchannel a spell is that instead of adding up the numbers on the damage dice, you use the maximum possible result. Most of the time this means there is no point to rolling the damage dice, but it doesn't say that you don't.

In Chaos Bolt's case, you'd roll damage as normal, using the type table and chaining mechanics as explained in the spell, but you'd substitute the rolled damage with maximum damage.

As an example, if you rolled 1, 2 (d8s), and 6 (d6), you would choose either acid or cold, you wouldn't jump to a new target, and you'd do 22 damage.

Answer 2

Dealing max damage is not the same as rolling max damage

According to the wording of the spell Chaos Bolt:

If you roll the same number on both d8s [...]

This effect occurs specifically when number on the damage die are the same. Compare to the wording on the Overchannel ability:

When you cast a wizard spell of 1st through 5th level that deals damage, you can deal maximum damage with that spell.

This doesn't apply to the damage dice, just the damage output, so no auto-chaining occurs as a result of using Overchannel. Compare this to another example that actually does change the roll value; the Rogue capstone ability Stroke of Luck:

Alternatively, if you fail an ability check, you can treat The D20 roll as a 20.

The question that then follows is, does using Overchannel even allow for Chaos Bolt chaining if no roll is made? That would probably be up to your DM, or worth its own dedicated question here. As GreySage's answer seems to imply, the roll is still made, just overridden.

Answer 3

It depends on what it means to "Maximize" damage

I've opened a second question to interrogate that question, so I'm not going to adjudicate that here.

For our purposes, we'll consider both of the scenarios that I'm aware of that could be valid interpretations of that word.

Scenario A: Damage is set to the maximum value that could have been rolled by all the dice

In this scenario, there's no automatic chaining. You still roll the d8s (and ostensibly the d6) as you normally would when rolling damage for the spell; you simply instead use the maximum value of 22 when actually applying the damage. The rolled values on the d8s are still used to determine the damage type, and whether or not the spell leaps to a new target.

Scenario B: Each die is set to its maximum value

In this scenario, then the Chaos Bolt will indeed chain from target to target automatically, until either

• The Wizard fails their Attack Roll, or
• The Wizard cannot find a new target within 30ft of their last target that has not been damaged by this particular casting of the spell

In this scenario, the spell will always deal Thunder damage.