I'd like to know if I can use the Heat Metal spell in the Baldur's Gate: Descent into Avernus module and target an Infernal War Machine.
And more specifically, what happens about this part of the spell:
If a creature is holding or wearing the object and takes the damage from it, the creature must succeed on a Constitution saving throw or drop the object if it can.
What happens to the passengers?
Can the pilot continue to pilot?
There are three reasons why this shouldn't work:
The Heat Metal spell description says:
Choose a manufactured metal object, such as a metal weapon or a suit of heavy or medium metal armor
If a creature is holding or wearing the object...
So it is not "any" object, but specifically an object "such as a metal weapon or a suit of heavy or medium metal armor", a thing that it supposed to or at least can be held or carried.
When adjudicating corner cases game designers suggest taking a couple of things in consideration: the description text itself, the common sense, the intention behind the spell:
"An illusory object made by minor illusion is meant to be like a stool or a rock, not an atmospheric effect." — Sage Advice Compendium, page 16.
The intention behind the Heat Metal spell is heating relatively small objects like weapons and armor, not ships, infernal war machines, giant metal fortresses, etc. If a DM allows heating vehicles, a mere 2 level spell becomes an effective anti-materiel weapon, which probably makes this spell a no-brainer (and no-brainers are bad design).
The spell reads:
Choose a manufactured metal object, such as a metal weapon or a suit of heavy or medium metal armor. If a creature is holding or wearing the object, etc.
Is the Infernal War Machine a manufactured metal object? Possibly, it depends on your definition. I'd go with 'no'. but even if you decide yes, read on.
Is somebody holding or wearing it? No.
A DM is free to change the spell to make 'being inside something' count as 'holding something', but this is opening the floodgates for weird gimmicky uses of the spell that weren't intended, like "I'll cast Heat Metal on the cage to damage everybody inside it".
Heat Metal may be cast on:
a manufactured metal object, such as a metal weapon or a suit of heavy or medium metal armor, that you can see within range.
The infernal war machines are manufactured and metal, so the only question is whether or not they are objects.
As it turns out, 'What is an object' is not an easy question in 5e rules. What is not an object is pretty clear - the machine is not a creature, or a spell effect, or a dungeon hazard, so it is definitely 'object-class'. But is it an object, just one object for the purpose of the spell, or is it a collection of many objects?
The DMG says:
For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.
The meaning of the second part of this passage in the DMG is: buildings and vehicles, when they are composed of many other objects, are thus not objects themselves. That is, a building or a vehicle might be an object or it might not; they are objects when they are simple enough, but not objects when they are composed of many other objects.
For example, a cart is a vehicle, and it is also listed in the DMG as a "large object", and it is composed of what were once many separate objects. It is composed of many objects (wheels, tongue, side rails, etc.), but not so many that it is not an object itself.
On the other hand, the ship rules in Appendix A of Ghosts of Saltmarsh, tell us that:
A ship is composed of different components, each of which comprises multiple objects:
Hull. A ship’s hull is its basic frame, on which the other components are mounted.
Control. A control component is used to steer a ship.
Movement. A movement component is the element of the ship that enables it to move, such as a set of sails or oars, and has a specific speed.
Weapon. A ship capable of being used in combat has one or more weapon components, each of which is operated separately.
These components are both "used" by the crew (through the Use an Object action) and have their own AC and hit points should something attempt to damage them. Even the smallest and simplest watercraft listed as an example, the rowboat, has two different multi-item components: the Hull and the Oars.
So are Infernal war machines more like carts or ships? They do have 'action stations' which resemble the components of a ship. The smallest war machine (the Devil's Ride) has just a Helm, while the largest (the Demon Grinder) has a Helm, a Chomper, a Wrecking Ball, and two Harpoon Flingers. In addition to these action stations, each infernal war machine has an engine and a furnace, which themselves appear to be 'components composed of multiple objects'.
However, unlike ships, a war machine has a single AC and hp total, meaning that its action stations and other components cannot be individually targeted by damaging effects.
Further consider that within the specific context of heat metal, one of the examples given in the spell description of 'a manufactured metal object' is a 'suit of heavy metal armor'. While typically sized for a humanoid, this could be as small as the plate mail of your Fairy PC or as large as your Elephant's plate barding. In terms of complexity, real world plate armors consisted of at least twenty individual pieces which were each put on separately, which is why it takes so long to don and doff the armor. We also know that some of these pieces, such as the gauntlets and helmet, are explicitly considered objects in their own right by the rules. Thus it is clear that the heat metal spell is designed to interact with an item that is both large and composed of many parts, while still treating it as a single object.
Within this context, I would say that the entire war machine should count as one object, for the purposes of effects that cause damage; thus the whole war machine itself could be targeted by, for example, a chain lightning spell. On the other hand, spells and other effects that can affect objects without causing damage would more appropriately be targeted at the specific components of the war machine. Thus when casting heat metal on a war machine, a caster should have to specifically choose a particular weapon station, or the helm, engine, or furnace.
Heat metal says (emphasis mine):
If a creature is holding or wearing the object and takes the damage from it, the creature must succeed on a Constitution saving throw or drop the object if it can.
Note that most of the passengers of a war machine, being devils, would not take damage from a heat metal spell, since most devils have immunity to fire damage. Thus they could maintain their seats comfortably even while their station of the war machine (which is itself immune to fire damage) heated up.
However, there are some passengers that might be affected - such as
the hobgoblins in the band of Bitter Breath
the PC's themselves, or perhaps a rival party of NPC adventurers.
In this case, the vulnerable passenger would find themselves on a superheated and damaging metal surface - but on the turn of the caster. In this case, "spells do only what they say they do" meets "the DM describes the results of your actions". Certainly if the passenger was at a weapons action station they would "drop" these controls, preventing them from using the weapon. Likewise, if they were "clinging to the outside of the vehicle" (BG:DiA 216), I think it would be appropriate for a failed Con save to then provoke a Dex save to remain on the vehicle, such as is described by the Mounting and Dismounting rules:
If an effect moves your mount against its will while you’re on it, you must succeed on a DC 10 Dexterity saving throw or fall off the mount, landing prone in a space within 5 feet of it.
However, if you were seated at an action station whereby you didn't need your hands to 'stay on' the machine, simply taking damage would not (in my opinion) be enough to force you to leap off the vehicle - especially if it was moving!
Similar to the discussion above of passengers, most pilots would be immune to fire damage and not be inconvenienced if the heat metal was cast on the Helm of the vehicle. For the rare vulnerable pilot, a failed Con save would certainly mean that they "dropped" the controls.
The heat metal spell says:
If it doesn't drop the object, it has disadvantage on attack rolls and ability checks until the start of your next turn.
I would interpret this as the pilot being at disadvantage to perform "stunts", canceling out the advantage from a "juke", and granting advantage on the save to a target of "crushing wheels" or "raking scythes".
By the description on page 216 of BG-DiA, An infernal war-machine is "manufactured" and "made of iron". Thus it is a manufactured metal object, thus a valid target.
However it also states that "An infernal war machines statistics function like those of a creature", meaning you could argue they count as creatures. So there is some DM discretion on whether or not to treat it like a creature. So ask your DM if they are treating it like a creature it is a valid target for creature targeting spells If they are not then it can be targeted by heat metal.
This could be argued both ways. It says, "like those of a creature", which would imply treat like a creature. But at the same time, function like a creature, would imply it is not a creature and it should be treated more like a wielded magic item.
Personally I would lean toward treating them as creatures, there is a balance aspect, many spells cannot target objects, limiting how you can fight one.
If treating it as a creature it cannot be a target for heat metal.
Now assuming your DM says they are treating it as an object, then some of your other questions can be answered.
Note that nowhere in the spell does it say the object takes damage so the vehicle itself will not be damaged if it is a object.
Can they continue to pilot it:
Well you can continue to holding a sword it has been cast on if you succeed your save, so you should be able to keep piloting if you make your save, you will just take damage every round. I would also argue that much like armor you keep taking damage is you stay inside it, so internal passengers would flee or take damage. External passengers can simply let go like a weapon of shield. But this gets into the gray area of what happen when you cast it on an iron ladder someone is climbing or on an iron cage with a prisoner? The spell leaves a lot up to the DM.
Yes, BUT Selectively
If you can target someones weapon in their hand, you could probably target a steering wheel on a War Engine.
Some war engines have a few weapons on then, each requiring a operator, so treating each weapon as a separate target for the purpose of the spell would make sense.
I don't think there is a "right" answer to this question as far as RAW goes because the wording is ambiguous, which usually means the real question is "is it right for my campaign?".
What you should ask yourself when answering this;
-Is it fun / would you be rewarding a cool idea?
-Is it balanced, would doing it to your players feel fair?
IMO, the answer to the first is yes, and to the second is no. But since the answer to the first is yes, is there a way to make it balanced? I've thought about this particular case because as the DM I wanted to do it to my players. I decided that it would take a tremendous amount of magical power to do this to so large a metal object in a way that actually injured players, so I decided to get even the base damage of Heat Metal it would need to be case at say, 6th level. ie; I'm not going to do this to a fledgling party, but if it's reasonable they're going to come up against Disintegrate and Chain lightning, giving them a flaming hot vehicle doing 2d8 a turn they have to contend with is totally reasonable and vice versa. The alternative would be to choose something like just the steering wheel/column, which will still mess them up pretty good. I think the mishap table is one of the most fun parts of the infernal war machine schtick.
Anyway, just my two cents. It's a fun idea, I'd let it happen, but I would make very clear that to make it balanced (and reasonable) it's going to work like x (where x makes sense for your campaign.
