We came across an issue in our game last night. We were ambushed in a system of tunnels and chambers, with monsters approaching from two directions.
The druid wanted to cast a Wall of Fire in a 30 ft circle around the party to give us time to think (and do some damage, hopefully, to anything approaching).
The problem is, how would this work within the cave system, as there isn't a 30ft clear space. See pic below:
Sorry for the sketchy quality, I'm drawing it from memory. Party is at the green cross, mobs are red crosses ahead of us and behind. Yellow/orange line is the Wall of Fire.
In the first pic, the WoF is a circle 30' diameter, but has been squeezed (like a bubble) into the space, so it lines the walls of the cavern. If the druid moved forwards, the WoF would squeeze out into the main chamber. If this is the case, should the enclosed area remain constant? (ie. in this image, it should be squeezed out further along the narrow tunnels and a little further out into the room? This would be consistent with the idea of a squeezed bubble...)
In the second pic, the WoF is a constant diameter ring, but only appears in the open spaces, ie. it just disappears inside the walls. OR, does it not disappear inside the walls? So if there was a secret room just to the top right of this map, would it be affected by the fire?
OR, final option that was presented (by the GM) the spell just fails if there isn't enough open space for it to be cast. The party didn't like this option, needless to say, because it seems to bring up future issues if we state we're not able to cast a spell at all if the area is too small.
The GM wasn't happy with either of these, so we didn't use the spell in the end.