Beguiling Defenses and Damage Resistance

This concerns the Warlock Archfey level 10 ability Beguiling Defenses.

If a monster’s damage consist of two damage types and I have the Beguiling Defenses, then I can reduce the damage by half. Then I also have damage resistance to one of the damage types. Beguiling Defenses comes first per the rules. If I take 70 slashing dmg and 30 fire dmg, That become 35 slashing and 15 fire, returning 50 damage. With fire resistance that is 35 slashing and 8 fire, i.e. 43 damage taken.

However, is this allowed? I first half the damage, removing only slashing damage, leaving 20 slashing and 30 fire. Then I apply fire resistance, taking away 15 fire damage, leaving 35 damage taken. Beguiling defenses does not teach how the damage is halved. 

This is one of those rather frustrating areas where there seems to just be a gap in the official rules. There's no general rule in the Player's Handbook about how damage reduction effects work against something that does multiple types of damage in a single instance, nor do any of the individual features that do this offer any specific rules on it.

To me, it makes the most sense to apply the reduction across both damage types — i.e., you halve the slashing damage and halve the fire damage — just because it's simpler and I feel like letting people choose how to distribute it would bog things down in the middle of combat. But I also think that, given the vagueness of the official rules, it would not be unreasonable for a DM to rule that you could arrange it however is most advantageous to you.

This kind of things has been debated recently for a similar feature: Rage, and Spirit Shield VS Mixed Damage Types

There is no a single way of ruling this. My humble recommendation: check out the thread and make your own ruling/verdict.

(another thread bring up a similar debate for "Level 3: Deflect Attacks": Damage Reduction and On-Hit Effects (page #2))

Just leaving my take here (split proportionally), along with another one from jl8e and Pantagruel666:

Quote from TarodNet >>

Yeah, that's why I mentioned you need some ruling to solve the issue with mixed damage types. 

One way could be to reduce/split the damage types proportionally.

Or following jl8e's idea:

• Attacker picks (AKA, reduce damage in the least advantageous way possible)
• Defender picks (AKA, reduce damage in the most advantageous way possible)

Quote from Pantagruel666 >>

While RAW is clear that reductions to damage occur before damage resistance, what it does not say is which damage should be reduced. As such, unless the ability specifies, I would allow the victim to decide.

EDIT: ups... ninja'd my wagnarokkr!

Just to add this good analysis here as well, from the same thread I linked:

Quote from AntonSirius >>

Quote from TarodNet >>

- If Spirit Shield is a bonus, shouldn't it be applied first? And after that, damage resistance from Rage:

Order of Application

Modifiers to damage are applied in the following order: adjustments such as bonuses, penalties, or multipliers are applied first; Resistance is applied second; and Vulnerability is applied third.

 

Yeah, the example given in that section makes it clear Spirit Shield would apply first, before any Resistance

For example, a creature has Resistance to all damage and Vulnerability to Fire damage, and it’s within a magical aura that reduces all damage by 5. If it takes 28 Fire damage, the damage is first reduced by 5 (to 23), then halved for the creature’s Resistance (and rounded down to 11), then doubled for its Vulnerability (to 22).

 

As far as I know, there's no guidance given in the rules on how DMs are supposed to do that for split damage types, so it's really their call. They have at least four options though:

• split the damage reduction evenly

Let's say the incoming attack does 5 fire damage and 10 slashing damage, and you roll a 6 for Spirit Shield. Splitting that evenly (3 and 3 to each type) would result in a final damage total of 2 fire plus 3 slashing (rounded down) = 5

• split the reduction proportionally

Instead of 3 and 3, the Spirit Shield would eliminate 4 slashing and 2 fire, and the final damage total would = 6

• split in favor of the attacker

All 6 points from Spirit Shield would go toward slashing damage, and the final damage total would = 7

• split in favor of the defender

The fire damage would be completely erased, with 1 extra point applied to slashing. Final damage total would = 4

At small numbers, the difference isn't that great. Against, say, a meteor swarm though...

There's no RAW answer here. You just have to decide what makes sense for your table

Thanks for your answers. I think it is good to be aware of the lack of clear ruling on this point, and the need for establishing a house rule. I think it makes sense for defender to decide, as the defender knows what effects, resistances and vulnerabilities the defender has. Furthermore, getting the most out of your defensive capabilities seems correct as a principle. Similar to how an attacker would seek to make the most out of his offensive capabilities. 

An argument against the defender decides would occur if you had an immunity. If you first could take away half of one type of damage and remove the other half afterwards due to immunity, that does not seem to be correct either. I guess the rules only specifies other effects, resistances and then vulnerabilities. From the look of it, immunities should be dealt with before anything else, then it seems to work from my perspective - i.e. defender decides.

I agree with you regarding Immunity, so I'd say it's part of "adjustments such as bonuses, penalties, or multipliers are applied first":

Order of Application

Modifiers to damage are applied in the following order: adjustments such as bonuses, penalties, or multipliers are applied first; Resistance is applied second; and Vulnerability is applied third.

This is from XGtE:

Resistance and Vulnerability: Here’s the order that you apply modifiers to damage: (1) any relevant damage immunity, (2) any addition or subtraction to the damage, (3) one relevant damage resistance, and (4) one relevant damage vulnerability.

Excellent, thanks for providing that reference to XGtE. This seems like a good basis for a house rule then.

Could you give an example of an attack that does multiple types of damage which are not defined?

Generally attacks do XX BPS and additional XX elemental (for lack of a better word) damage. In which case it is easy to say which damage is halved or doubled.

For example, the one provided by AntonSirius:

Let's say the incoming attack does 5 fire damage and 10 slashing damage, and you roll a 6 for Spirit Shield. Splitting that evenly (3 and 3 to each type) would result in a final damage total of 2 fire plus 3 slashing (rounded down) = 5

Or:

Balor: Flame Whip. Melee Attack Roll: +14, reach 30 ft. Hit: 18 (3d6 + 8) Force damage plus 17 (5d6) Fire damage.

The tricky part is when you have some Resistance and Vulnerability.

Thank you very much for contributing with the related cases in the rules and for this example.