Is there a minimum intelligence score needed to make use of non-natural abilities?

Question

In a recent session a character who was under the influence of a Potion of Flying was turned into an ant by a hostile spellcaster. The DM rules that even though the potion's effect persisted and gave the ant a 60ft fly speed, the character could not use the fly speed because "an ant doesn't know how to fly and isn't intelligent enough to find out." He later clarified that the ant was specifically a worker ant and as such doesn't naturally fly in its life cycle.

I find this to be unconvincing. While polymorph states that "The creature is limited in the actions it can perform by the nature of its new form", the Fly spell or Potion of Flying isn't dependent on the natural form of the creature it targets to begin with. Ants are able to move of their own will and nothing in the spell description states that creatures need to learn how to use the fly speed they gain (after all, humans also cannot fly by nature).

I also find it problematic to assume that polymorph can render a character unable to use their buffs, even though it nowhere states that it interferes with other magical effects. I phrased the question in a nonspecific way, because this would just as much go for a potion that, say, allows the character to breathe fire or breathe underwater. The effect doesn't specify that the character needs any kind of special training or skill to use it, it does not involve spellcasting but describes a relatively straightforward physical action like breathing or moving.

Nonetheless, I also can see the point that certain actions or decisions could be expected to require a certain value of intelligence or wisdom to perform or conceive of. Is there any guidance on the rules as to how a character whose intelligence is reduced below human levels or whose form is changed to one with low intelligence can still act and which abilities beyond the natural and instinctive they can use? Is there anything about whether effects that give the character a new ability automatically imbue them with the knowledge of how to use them and whether this requires a minimum mental ability score to work?

Answer 1

This comes down to two completely different principles, both of which apply, and a comment on DMing well.

Things do what they say they do.

The Potion of Flying adds a fly speed to your statblock. That's what it does. If your statblock is that of an ant, and you're affected by a Potion of Flying, then you're an ant with a fly speed, and there's nothing about fly speeds that makes any reference to intelligence (Indeed, it's quite clear that one can fly with only insect levels of intelligence.)

Rule zero is a thing.

5e specifically calls out that the DM is permitted, and, indeed, encouraged to make houserules and adjudications. It leaves unclear spaces in its rules so that DM adjudications will be called for. (This isn't a particularly strong case of one, but they're there.) If your DM has adjudicated something, then that is, indeed, the way things work in your game.

This particular ruling was probably a poor choice

The game works better when you let your players be awesome. Using Rule zero because something spontaneous happened and you want to let your players do the awesome thing that makes sense even if it breaks the rules a little is using it in the best way. Using it to further dump on someone after you've shut them down almost completely by turning them into an ant is not.

Honestly, if a PC manages to leverage "being an ant with a fly speed" into somehow pulling off something awesome, you should let them. (...unless it was just "I'm going to kill myself so that I depolymorph". That one's not particularly cool.)

In general, though, if the DM says that that's the way it works, then at their table, that's the way it works. If you're looking for the broader "How does it work in the abstract, before any DM gets their hands on it?" then the answer is that an ant with a fly speed can fly.

Answer 2

No, there is no such minimum necessary ability score

The RAW to read RAW is to start with: there aren’t secret rules - if it doesn’t say it, it doesn’t do it.

There is no general rule tying low Intelligence to any restriction on action. As such, any such restriction would have to come from the specific effect; for example, the rules on multiclassing have such restrictions.

More generally, players have control over their PCs. Playing a PC who has an Intelligence score of 3 as consistently having brilliant ideas may be mis-matched role play, but it’s not against the rules. The player decides what the PC does; stats are only relevant when the rules say they are - for example, when making an ability check.

A potion of flying gives a creature a fly speed without restrictions. No ability checks are required for example.

The polymorph spell says:

The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast spells, or take any other action that requires hands or speech.

Flying is not explicitly proscribed, so it depends on the “nature” of an ant that has, through a potion of flying, a fly speed.

My ruling would be that an ant with a fly speed can use it.