I've been looking through spells trying to find a good Wall spell for my BBEG wizard, and I come across this beauty: http://www.d20pfsrd.com/magic/all-spells/w/wall-of-brine-merfolk/.
Now, on the one hand, it doesn't look too amazing. No damage, no solid blocking effect. On the other hand, four squares of movement (five, actually, since you need to move out) is a pretty hefty speed-bump unless you've Haste up, and look at that area! Ten feet a level in length, insane height, and it's shapeable!
So, anyone ever used this? Any thoughts? I'm trying to think of a way to make it double-back so you can make a double-thickness wall, but sadly in that case the current would go in opposite directions, rendering it somewhat moot.
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does seem like pretty good blocking terrain - pity you've gotta be merfolk to cast it (probably - ask GM). if you could make it double back twice so they've gotta go through 2 in the same direction that'd work to stop most things getting through in 1 turn
Well, in this case I *am* the GM, and I tend to allow most racial spells unless the effect itself ties into the species.
Sadly, I don't think the physics of it work for double-thickness walls, though.
You might consider layering walls if you think the BBEG can buy the time. First get a wall of brine up, then a wall of nausea in front so they might have to make the save 3-4 times. And any ranged attacks have to deal with cover and concealment. Another possible way to make this setup harsher is to throw in some difficult terrain spells before or after casting wall of brine. Many spells have obvious offensive uses and create difficult terrain (Ice Storm, Black Tentacles, Stone Call, Sleet Storm, and Obsidian flow to name a few). This would make breaching the wall nearly impossible barring haste/flight/other movement boosters.
Remember that you can see through the wall. This means you can do fun things like summon monsters on the other side of the wall to preoccupy the PC's while the BBEG does other work with the battlefield.
Doubling up on the wall probably wouldn't work, but you could use it to create a flank-proof zone for your wizard (back up into it, nobody can really stop in the wall for long enough and if a retreat was needed, it doesn't block your escape. You could also use effects like waves of blood to help move approaching PC's out of reach. You could also decide to houserule that the spell causes water to flow in a direction (N, S, E, W, etc) so that doubling the wall up could work. Of course, keep this ruling consistent if any PC's decide to research Wall of Brine for themselves.
Overall, this looks like a really need terrain-blocker spell as long as you are willing to work with it, but standing alone its not particularly better than some of the already-available options (Wall of Ice being the most relevant for being the same level, a similar theme, and actually being a solid wall).
My rough idea was that the BBEG would start off by dropping a big-nasty bad-zone on the PCs (think Hungry Darkness, Sirocco, etc). Then put up a Wall of some sort to restrict the battlefield. So I've been looking through wall spells -- I rather like Wall of Ice, but for the 'fails if even one person makes a Reflex Save'. Then I found this, and it certainly does seem like it would slow the PCs down quite a bit.
I definitely like the Waves of Blood idea and the anti-flank zone. I myself was thinking it would combo nicely with Quickened Hydraulic Push.
And the houserule idea I have toyed with, though I always run into a problem with such things (I always make rules equal-opportunity, as a point of honor). If I announce the houserule only when the Brine Wall shows up, I feel somewhat cheap for springing that on the players. "Oh, here is the antagonist using a spell, and I have made it EVEN BETTER!" On the other hand, telling them ahead of time is basically sending up giant red flags. Tricksy problem.