First off, none of my players had better be reading this. If your PC is named Arilla, Karthas, Ni'shand, or Shade, beat it.
Now that we're comfortably alone...
So, in my campaign a Sodkiller fortress is going to come under attack by a disenfranchised bounty hunter on an ego trip. The fortress is on Acheron and I thought it'd make for a great moment for the villain to arrange for his target, a Sodkiller high-up, to eat it by being crushed in a cube collision. In order to give the PCs a fighting chance at rescuing their patron, I'd like to not simply flatten the entire cube face like an ant under an iron golem boot.
Any ideas?
How much warning time do they have and what level are they? They could do a massive rush for the Sodkiller to teleport him out in the nick of time.
Or if lower level, start escorting (read:running) him towards a conveniently nearby set of tunnels into the interior of the cave. That also gives you the opportunity to run them into some very claustrophobic stalking scenarios with low supplies since they would have had to book it with only what they had on hand.
I can't really think of any ways to make the collision not occur once it was triggered - walls of force *do* have a break point as far as I recall.
I may be more interesting to make it a trap - play up the idea that the Sodkiller's are running military actions here. Let them see the orrys and maps that they use to track when cubes are epxpected to collide so they can avoid it. Maybe let the SK go off on patrol and then let one of the PCs realize that their maps and orrys have been tampered with so they have to find a way to contact him to get him to avert course post haste.
Or if they do go out with him in the column, have them start making spot and intelligence checks to realize that the cubes aren't moving the way they're supposed to... (and then go with that 'run for it' option as posted above?).
If the entire cube is made of lead (blocking some divination attempts) or some other material that'll block teleportation... or your big bad enscribed a freaking *huge* symbol of 'dimensional anchor' on the other cube that now is locking your victi-ahem-party inside the first one for as long as the cube remain in contact... I'm sure you can see where I'm going with that.