Firstly, a quick anecdote. In our most recent Pathfinder session our cleric jokingly mentioned he will soon be able to summon 1d3 dolphins. Another player then mentioned that some dolphins (orca) can weigh up to 10 tonnes. We then had the great idea of dropping them on top of enemies; in particular, by combining this with the Fly and Hold Person spells. 1d3 x 10,000kg dropping from 100m up is a lot of kinetic energy.
Of course, the GM quickly forbade this (luckily we had no cause to put this plan into effect). But this got me curious: what should a GM do when players find ways of using magic in unexpected and potentially game-breaking ways?
Some attempts to 'fix' the problem, and why they won't always work:
- The GM can ban the spell.
- But then the players lose the intended functionality of the spell as well. If it's a particularly relied-upon spell (e.g. healing or resurrection) then the players are at a disadvantage for being creative.
- And what about NPCs/enemies? Do they lose the spell? If not, the players are at a disadvanteage. If so, won't the NPCs be unbalanced due to losing a spell they relied on?
- The GM can (sometimes) make the act impractical. Using the above example, the GM can simply rule that the dolphins are small and weigh very little.
- But sometimes the GM doesn't have that kind of wiggle-room. If our cleric were, for example, to summon a horse then we'd expect it to be the size and weight of a regular ride-able horse. And other spells might be even more specific.
- If the GM does make a ruling, this exception to the normal rules could itself be exploited. E.g. if the GM decreed our summoned horse weighs very little ("and is now impractical to drop on enemies, ha!") but it takes up the same volume, wouldn't it be extremely buoyant? So we couldn't drop the horses on people, but we could (as an example) use them to run across water?
- The GM can threaten alignment penalties, having allies forbid the act, etc.
- This isn't always an option. If the usage of the spell doesn't violate your alignment in any way other then being unusual then it would be unfair to penalize the player.
- Similarly, if the spell defeats the evil dark lord, why would allies forbid it? A mildly nasty act (sacrificing a defenseless dolphin) is certainly preferable to risking the lives of the villagers.
- The GM can ban the use of the spell "in that particular way", or simply say "it doesn't work."
- This is a frustrating cop-out, and won't stop certain types of players from experimenting with what they can get away with.
- E.g. if our cleric can't drop dolphins from 100m up, can he drop them from 10m? 5m? 1m? Can he summon dolphins on top of a battlement and then push them off?
So what can a good GM do? What should a good GM do? Not in regards to my specific example, but regarding unusual abuses of magic in general? Note that our players aren't trolling the GM or anything; they're simply too creative for the setting/ruleset to cope with.