One PC of the game I am currently hosting has the spell "aboleth's lung". In short it means, that any land creature cannot breathe air anymore, but only water. This lasts one hour. Of course she will use it as a weapon against some enemy, be it a dark elf, a minotaur or any other creature.
What are your suggestions to decide how long an enemy can still fight holding their breath? A minute (10 rounds)? A few seconds (1 round)? Are there any written rules for that?
Best Answer
Suffocation:
Although the medium he breathes has changed, a victim of aboleth's lung is going to suffer the same fate unless he reaches water.
An Aside: On the Cruel Nature of the Spell Aboleth's Lung
The spell aboleth's lung is a 2nd-level, slow save-or-die touch spell versus foes without dispel magic and who breathe. That's... actually a lot of folks, especially at low levels. That the creature dies faster if it tries to murder the caster is tasty gravy.
The problem with the spell is when it's used versus the PCs. It's entirely possible for PCs to face foes who can employ the spell when the PCs are among the folks vulnerable to it, making it just a slow, unpleasant death sentence. Such spells are unusually unfun, making players feel helpless while also killing their characters. Usually, it's more fun--as the DM or the player--to just cast scorching ray at a dude than to slowly suffocate him while making him do math.
There's an argument that adventurers should be carrying water when adventuring, giving them the means to save their air-drowning friend. But this assumes someone trained in the skill Spellcraft successfully identifies the spell when it was cast. (Pathfinder removed from the Spellcraft skill the ability of D&D 3.5's Spellcraft skill to identify a spell that’s already in place.) If the Spellcraft roll's failed, the DM just describes the spell's effects--suffocation. Uninformed PCs are then supposed to make a leap of cartoon logic that shoving their friend's head underwater will save him, which makes about as much sense as stopping bleeding by sticking a sword in the wound.
The spell, without DM's permission, is supposed to be exclusive to gillmen. Encourage your players to enter into a gentleman's agreement wherein this spell's just used by gillmen... then don't use gillmen. The spell aboleth's lung is a war crime.