Heat Metal is a 1 action casting 2nd level concentration spell which damages someone holding or wearing a manufactured metal object.
It has a range of 60 feet. Which will be relevant to this conversation.
It does 2d8 fire damage each round the caster uses a bonus action to cause that damage. It lasts for up to 1 minute. So over 10 rounds that's about 90 HP damage.
The spell is frequently cast on PCs wearing heavy armor. Heavy armor cannot be removed within the 10 rounds, even with help. There is no save to avoid this damage for armor you're wearing (there is only a save to hold onto a weapon rather than drop it.)
Here's the key: The spell does not specify you need line of sight, or need to stay within range, during the duration. And the rule for that kind of spell in the Player's Handbook is, "Once a spell is cast, its effects aren't limited by its range, unless the spell's description says otherwise." There are some spells which do include in the description that it ends if you move out of range, such as Witch Bolt which says, "The spell also ends if the target is ever outside the spell’s range or if it has total cover from you." But spells like Heat Metal don't include that kind of description and are similar to the Sleep spell where, once cast, you just stay asleep even if the caster leaves line of sight or range.
Which means a caster can just cast this spell on someone in heavy armor and just run away. As long as they expend a bonus action every turn while they flee, the target will eventually take 90 HP damage from this second level spell. They could even teleport away. I think they could even go to another plane of existence and the still would continue to do the damage for the full minute?
The reason I think the spell might be unfair is because it's particularly damaging to PCs in heavy armor. Yes, of course it could be used by a PC on a foe, but the odds of running into a foe in heavy armor is typically pretty low. Most casters who can prepare the spell, choose not to because they go too many days without being able to use the spell as effectively as other second level spells.
Which means this spell is more often used by enemy spellcasters. And it's most often used by them against PCs with heavy armor, if they're around, because they cannot remove that armor in time to avoid any damage.
It's already not particularly optimal for a PC to wear heavy armor given its cost, strength requirement, speed reduction, stealth reduction, fact that you can't easily wear it while long resting, etc. Players who make PCs with heavy armor are often already doing it for aesthetics and could have possibly made a slightly more effective PC focused on Dex instead (even if it's just a 14 Dex and medium armor). This spell is often, by the circumstances of actual play, likely punishing those heavy armor Strength based PCs further for being a Str based PC in heavy armor. And I don't like that.
How do others find this spell to be in their games?
The key issue you didn't mention there is that it's Concentration-based.
So if you can break their Concentration, the spell is gone.
And the vast majority of enemies who cast this spell, are fairly easy to break Concentration on. I can't think of any enemies with Advantage on CON saves, or similar stuff that would protect their Concentration the way some PC casters can do it too.
As for the "running away" strategy, the issue that's massively sub-optimal, tactically. You're abandoning all your buddies to get killed, in the hopes that maybe you do enough damage to kill a PC. If you stuck around, you could still do damage, still cause a distraction, and so on. Your side's overall performance would be much, much higher. It's essentially a 1:1 sacrifice
at best. It's very likely, with magic in the equation on the PC side, that you don't kill them. Fire Resistance (the most common resistance, fairly routinely possessed by PCs) or Absorb Elements (a level 1 spell) both halve the damage, and turn it from a 90 HP murderer to a 45 HP "ouch but I lived" scenario (pretty sure there are CR1 monsters that with a crit or three can do 45 damage in a single round, let alone ten). Dispel Magic stops it dead.
On top of that, running away is hard in D&D, unless you just bomb it immediately. And again, if you do, you effectively died for purposes of that combat. You will have no further impact beyond that 2d8/round damage, when if you'd stuck around, you could do 2d8/round + whatever attacks you made (plus people trying to kill you so letting the other enemies live longer).
I've used it from NPCs, but never had it last more than two rounds, because PCs always, without fail, break Concentration on the caster. They jump on it. And NPCs running from PCs is like the mailman running from a dog. They will chase. They will throw EVERYTHING they've got into catching you, and every ranged weapon and spell will IMMEDIATELY target your butt for running. (This is because players know any NPC who runs during combat is very severely "up to no good", and thus goes to the top of the "aggro list" lol)
Breaking Concentration is extremely easy - damage, various conditions, or death all break it. So I don't find it to be the huge threat it in theory could be.
2) I do allow for some counters to the spell. Applying water or some other cooling agent will suppress the damage for 1 round. So simple submersion will stop the damage, if it's expedient. I also allow the control flames cantrip to halt the damage, again for 1 round. So repeated casting can also stop the damage.
Yeah exactly. We're playing an tabletop RPG with a DM for a reason. If you can stand in a lake or pond like an overheated Battlemech, you're going to make a lot of bubbles, but you shouldn't be taking damage from this, and I like the idea of making Control Flames more useful this way lol.
I've personally found the spell to be a death warrant for the NPC who casts it, so I do have NPCs cast it on heavy armour wearers, but only if I accept the NPC likely won't live to see the next round.
it all balances out.
