For the last couple encounters before my wedding hiatus, I wanted to run something interesting and complex in the vein of some of the combat/skill challenge combinations from the beginning of the adventure. The concept I started with was a prismatic wall, and then I tried to figure out how to make it a dynamic encounter element so it might actually see some use during the encounter.

I had a sort of one-man brainstorming session — I suppose it technically isn’t brainstorming if it’s just me, but I like to pretend that I can anyway — and I figured on working with some details I’d already dropped and some conclusions the party had already arrived at. The setup had the party breaking a siege, in the school, of one of the fortified libraries where the students had taken refuge.

The party had broken through the first (two) layer(s) of defenders and one of the players said (I don’t know if he even remembers) “we’re too late,” when he saw that the wall had been breached and enemies were pouring out. It had originally been my intent to assume there were simply thicker walls or additional rooms to plow through, but if I wanted to stage an entire other encounter, I’d need more room than that.

So, I figured on an additional section of insulating wall, tucked away in an extradimensional space, sandwiched between two normal sections of wall. There was an overlapping prismatic wall inside, and with the compression of space in effect, the wall was actually stretched out over the entire battlefield (one layer every 15 feet).

As a minor action, a character could make a difficult Arcana check to “open a door” through an adjacent section of the wall, allowing other characters to slip through — but being forced through the layer resulted in 6d10 damage of the appropriate energy type. (Half damage for making melee attacks through it.)

The first layer (red) did fire damage, and once the threshold was crossed, fire-based effects no longer worked (including the group’s firestorm arrows). The second layer (orange) dealt and negated acid damage. Yellow dealt/negated lightning, green worked against poison, blue worked against cold, and indigo/violet worked against psychic. The last layer, drawn in with pink … I never did decide what it could do.

The fight itself took place across the entire map, which as you can imagine, was quite large. I used terrain with variable heights, so at some points characters and creatures were climbing/bull rushing each other through the prismatic wall, and/or over ledges where they would have to climb back up to rejoin the fight.

I think the most devastating ability proved to be forced movement. One of the creatures I used could yank players 5 squares with one attack and its basic attacks would slide them 1 square, resulting in some truly spectacular damage if they were forced through the wall more than once. Still, between our two leader characters, no player character fell unconscious.

It was terribly all good fun.