This question came up when the spells wall of fire and blade barrier were cast and we weren't sure how to handle it. Described below are the issues we had, but first the relevant portions of the spell descriptions:
Wall of Fire has an Effect entry that says, in part, "opaque sheet of flame up to 20 ft. long/level". This sheet is hot enough on one side to cause damage, thus placement of the sheet can be very important for tactical reasons. It's pretty clear (although a derivation is beyond the scope of this question) that the "sheet of flame" must start at a given grid intersection and continue straight to another intersection.
The Blade Barrier spell also contains an Effect entry that says, in part, "[a] wall of whirling blades up to 20 ft. long/level".
These are the issues we found:
- If the sheet from the wall of fire spell is razor thin, as the word "sheet" implies, how far does the heat extend when the sheet partially passes through a square? For example, say 50% of the square is on the cool side of the sheet and 50% is on the hot side -- which squares cause heat damage?
- For blade barrier, how thick is the wall? Should it occupy an entire 5-foot square? If it did that, wouldn't it be an Area instead of an Effect, since the former is used to describe spells that occupy squares on the grid? And how would that affect the ability to create a ring out of the blade barrier? The description uses the phrase, "vertical curtain of whirling blades" so should it also be razor thin, just as the wall of fire is?
- Blade barrier says if the barrier is evoked so that it appears where creatures are, each creature takes damage as if passing through it. But if it's razor thin and the barrier is placed along the X or Y axis of the grid, then it doesn't actually occupy any squares, does it? Would creatures on either side be damaged?
- Why does a creature moving through the barrier get a Reflex save for half damage, when a creature who has to suddenly jump out of the way gets a Reflex save to take no damage at all? Maybe this is backwards?
- Can a creature perform a melee attack through the barrier (such as with a longsword) without requiring a Reflex save? After all, the spell says the save is necessary when moving through the barrier. Or would that only apply to reach weapons?
These are just the major problems we had. Other more minor issues came up but I think if these are answered the others will be as well.
I'm currently going through and updating my "house rules" document. Your input is appreciated. :)