Suppose that the mages Mary and Merry both cast Heat Metal at 2nd level on the metal armor of an enemy fighter, Fred. Both mages use their bonus action on subsequent turns to continue dealing damage to Fred. How much damage does Fred take each round, and when does he take it? What additional effects does Fred suffer, and how long do they last? For the sake of argument, let's say that the initiative order each round is Mary, Merry, then Fred.

  • \$\begingroup\$ Is there a specific interpretation of the spell you would prefer? "How does the secondary effect of the Heat Metal spell work?" \$\endgroup\$ Commented Nov 27, 2019 at 18:56
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    \$\begingroup\$ @Medix2 I'm not sure there's one I prefer. I guess you can answer generically, saying that Fred suffers "whatever happens on a failed save". \$\endgroup\$ Commented Nov 27, 2019 at 19:03

1 Answer 1


Only one takes effect at any time

The spellcasting rules address this type of scenario in the "Combining Magical Effects" section:

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect - such as the highest bonus - from those castings applies while their durations overlap, or the most recent effect applies if the castings are equally potent and their durations overlap.

This rule is reinforced in the Dungeon Master's Guide, under "Combining Game Effects" (p. 252, added in the DMG errata):

Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap.

In this specific case, only one casting of heat metal will have any effect. This is because the duration of the one Mary casts overlaps with the duration of the one Merry casts (they both have a duration of 1 minute).

Which one is the "most potent" will depend on your GM's interpretation. One could use such measures as spell slot used or spellcasting ability modifier. If the GM determines that they are both equally potent, the most recent casting's effect applies.

  • \$\begingroup\$ Is it really this simple? The 2 Heat Metal spells deal damage at different times. Are you saying that if Mary's Heat Metal deals 2d8 damage on her turn, then Merry's Heat Metal deals no damage? \$\endgroup\$ Commented Nov 27, 2019 at 18:59
  • \$\begingroup\$ @RyanC.Thompson Compare it to this question: If you cast Blindness/Deafness on the same creature twice, what conditions are applied? Even though the castings do very different things, only one applies. \$\endgroup\$ Commented Nov 27, 2019 at 19:00
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    \$\begingroup\$ @RyanC.Thompson It's really that simple. one spell has no effect until the other one ends. \$\endgroup\$ Commented Nov 27, 2019 at 19:01
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    \$\begingroup\$ @RyanC.Thompson It still depends on the GM's meaning of potent. It could mean a number of different things. \$\endgroup\$ Commented Nov 27, 2019 at 19:06
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    \$\begingroup\$ The solution to this is have one caster target a weapon while the other targets armour. Hmm actually maybe that's not even enough... \$\endgroup\$
    – Jason_c_o
    Commented Nov 27, 2019 at 19:09

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