Mechanics for Matalotok and the White Dragon Mask

Question

I am DM for my group, and I have plans to provide the Minotaur fighter of the group with this combination of magic items later in the campaign, and would like to confirm how the mechanics for the two work together.

Matalotok is a warhammer from Baulder's Gate: Descent into Avernus, and its relevant ability is:

You are immune to cold damage while holding Matalotok. Whenever it deals damage to a creature, the hammer radiates a burst of intense cold in a 30-foot-radius sphere. Each creature in that area takes 10 (3d6) cold damage.

The White Dragon Mask is from Rise of Tiamat (the online supplement I think), and the relevant portion of its abilities is:

Damage Absorption You have resistance against cold damage. If you already have resistance to cold damage from another source, you instead have immunity to cold damage. If you already have immunity to cold damage from another source, whenever you are subjected to cold damage, you take none of that damage and regain a number of hit points equal to half the damage dealt of that type.

With that out of the way, my question is this: If you attack and deal damage with Matalotok, the burst of cold damage that is released upon dealing damage, if not for the cold immunity, would that damage apply to the wielder of the weapon, and would that interact with the Damage Absorption from the White Dragon Mask?

My thoughts are that they would work together like so:

• Fighter attacks enemy
• Fighter hits enemy, dealing damage
• Matalotok does burst of cold damage
• Fighter is immune due to Matalotok
• White Dragon Mask turns immunity into absorption
• Cold burst hits fighter because it is in the radius
• Fighter heals for half of the cold damage dealt

Is this the correct way these items would interact, or am I interpreting this interaction incorrectly? Would Matalotok deal the "damage" to the wielder in order to trigger the Dragon Mask?

Answer 1

Yes, that is how it works

The weapon says: "the hammer radiates a burst of intense cold in a 30-foot-radius sphere. Each creature in that area takes 10 (3d6) cold damage." The fighter is in the sphere and therefore takes the damage.

The mask says: "If you already have immunity to cold damage from another source..." and the wielder does already have immunity to cold damage from another source, so the life gain effect triggers.

This is pretty broken

This is a combination of two extremely powerful effects and might have bad consequences for game balance.

In particular, you might get into situations where the fighter winds up doing combats solo, because (1) the healing effect from the weapon makes him harder to kill than normal, (2) the high damage from the weapon makes him much more effective than normal, and (3) none of his allies want to stand near him because they don't want to suffer the aoe cold damage.

This might not be fun for your group. I recommend being careful.

Remember that you can use Rule Zero

As the DM, you're allowed to create custom magic items.

If you wanted the group to find "a warhammer that's just like Matalotok from Descent Into Avernus except it doesn't deal its cold damage to the wielder", you could narrate that they find it. Nobody would argue -- making up magic items to give the group is literally your job.

(You'd probably want to give it a better name, of course.)

If you wanted to give the group a combination of magic items, but you wanted them to interact in a specific way, you could do that too. You could say: "the DM is allowed to interpret how magic items interact, and in this case the White Dragon Mask doesn't turn immunity into absorption." Your players might argue a bit, but you're completely allowed to do this.

You're allowed to narrate effects onto existing items, too. You could narrate that this version of Matalotok especially hates dragons, and it refuses to confer its immunity on anyone that wears the white dragon mask. Perhaps Matalotok is an ancient item with a long and storied history, and it wouldn't be surprising if it had a few quirks.

If you understand that you can issue house rules, and you're just trying to understand how the existing rules would work -- that's fine, we get you. But sometimes people come here with questions because they feel like they're obliged to strictly follow the Rules As Written and never make anything up. So it's often helpful to add a disclaimer that the DM isn't actually bound by the rules.

Answer 2

Yes, it is correct.

The warhammer Matalotok grants immunity to cold damage, which fulfills the "Immunity to cold from another source" requirement from the White Dragon Mask for the Damage Absorption ability to function.

I hope your players get this combination of items at a very high level :)