This seems to be a crash persistent across many versions of Forge- tried 54, 65, 76, and 87 (yes, I used the patcher/installer), tried updating Java, tried pulling JVM arguments. Forge is the only mod that's installed and running; I've been fiddling with this problem to get the Arisen modpack to work to my tastes, but again, no mods installed but Forge. Don't freak if you see folder paths about that.
Crash happens as follows- approach close enough to a potion spawner (you'll find these in custom maps, Chimarian Memories 1 or 3 has one close to spawn, for example) that it starts spawning potions. Crash. There is no crash with straight vanilla Minecraft.
Here's the pastebin to the full forge crash: http://pastebin.com/2rtupMP6
And the point of failure if you don't want to go through the full log:
I dunno if I'm missing anything, but I'm pretty savvy about navigating mods or crash reports, so let me know what else I can provide.