Rules question about Grave Domain's Channel Divinity

[jaappleton]

Here it is word for word:

"Channel Divinity: Path to the Grave
Starting at 2nd level, you can use your Channel Divinity to mark another creature’s life force for termination.

As an action, you choose one creature you can see within 30 feet of you, cursing it until the end of your next turn. The next time you or an ally of yours hits the cursed creature with an attack, the creature has vulnerability to all of that attack’s damage, and then the curse ends."

So, what if the target typically has Resistance to the damage type?

Specific overrides general. So in this instance, lets say the target has resistance to nonmagical Piercing damage. If its targeted with Channel Divinity, it gains Vulnerability. Its then shot with a normal crossbow.

Vulnerability, ignoring its resistance?
Or double the damage after resistance?

[Ganymede]

Here it is word for word:

"Channel Divinity: Path to the Grave
Starting at 2nd level, you can use your Channel Divinity to mark another creature’s life force for termination.

As an action, you choose one creature you can see within 30 feet of you, cursing it until the end of your next turn. The next time you or an ally of yours hits the cursed creature with an attack, the creature has vulnerability to all of that attack’s damage, and then the curse ends."

So, what if the target typically has Resistance to the damage type?

Specific overrides general. So in this instance, lets say the target has resistance to nonmagical Piercing damage. If its targeted with Channel Divinity, it gains Vulnerability. Its then shot with a normal crossbow.

Vulnerability, ignoring its resistance?
Or double the damage after resistance?

Multiply the damage by 2/2. Or, if you don't want to deal with perfunctory math, the attack does damage as if there was no vulnerability or resistance involved.

[Marcloure]

As per Jeremy Crawford (https://mobile.twitter.com/jeremyecrawford/status/930576764148924416), you apply both. First you divide the damage, then round it down, then multiply by 2.

In other words, they both apply, canceling out each other unless the damage is odd. If it's odd, then the damage taken will be one fewer (particularly, I say to you ignore this).

[Ganymede]

As per Jeremy Crawford (https://mobile.twitter.com/jeremyecrawford/status/930576764148924416), you apply both. First you divide the damage, then round it down, then multiply by 2.

In other words, they both apply, canceling out each other unless the damage is odd. If it's odd, then the damage taken will be one fewer (particularly, I say to you ignore this).

I don't get why it has to be done in that specific order. Why not vulnerability first then resistance? I'm not seeing it in the tweet or the rule reference.

Edit: There might be an errata not printed in my PHB.

[HappyDaze]

As per Jeremy Crawford (https://mobile.twitter.com/jeremyecrawford/status/930576764148924416), you apply both. First you divide the damage, then round it down, then multiply by 2.

In other words, they both apply, canceling out each other unless the damage is odd. If it's odd, then the damage taken will be one fewer (particularly, I say to you ignore this).

That just seems unnecessarily complex. If Advantage & Disadvantage can simple cancel one another out (you don't roll three dice and take the middle valued one, instead you just roll the one die) then that same logic should have been used here.

[jaappleton]

Damn. Was really hoping it’d cancel out any resistance. I get why it doesn’t, but... Still hoped.

[Slybluedemon]

That just seems unnecessarily complex. If Advantage & Disadvantage can simple cancel one another out (you don't roll three dice and take the middle valued one, instead you just roll the one die) then that same logic should have been used here.

Thats how i handle the Channel Divinity in my games, If the cleric uses it on a monster but the monster has resistance, the attack is treated as if the monster did not have resistance

[sophontteks]

Its really bad style to round down before the equation is finished. We round down because we don't deal with fractions of HP, something that is not a factor until we hit the final number.