My low-level PCs are going to be travelling to a layer of reality where things visibly exist in more than three dimensions. Creatures will move along unpredictable paths, there will be portions of objects and monsters invisible (and incorporeal) to the still-3D PCs, things will seem to have too many faces picasso-style, and so on. I'll be using a mechanic for attacking the monsters where they basically have total concealment (50% miss chance) at all times due to their extradimensional natures, as long as the PCs are attacking with normal weapons. The PCs can see that the creatures don't conform to normal standards of dimensionality but can't perceive or comprehend the differences well enough to adjust their fighting styles.
The PCs are going to acquire weapons crafted by a traveller from this dimension, which will function effectively against the creatures within it, removing the 50% miss chance. All well and good.
I'm at a little bit of a loss as to how these weapons will affect creatures on the Prime Material Plane, though. The obvious thing would be to give them a 50% miss chance, but I want the weapons to be useful in the real world too. The idea is that even on the PMP everything exists in these extra dimensions, but simply cannot be perceived as such.
I'm thinking something along the lines of one or more of these attributes, but don't know which ones to pick or how to balance them to end up with the equivalent of a +1 weapon:
- Increased critical range (due to wounding the creature's extradimensional portion)
- Chance to ignore armor and allow an attack against touch AC (but not always)
- Maybe a combination of the two - rolls to confirm crits can be made against touch AC?
- Perhaps a penalty to hit
- Decreased critical range, increased critical multiplier
- Occasional miss chance
- Able to hit incorporeal creatures (but perhaps not get over the damage halving)
- Anything else that you guys can come up with
This is a low-magic campaign, and these weapons will be the first real non-mundane weapons that the PCs have access to. A lot of the creatures in this realm (which I think of as "Sevenspace") are based on sea creatures for an alien feel, and the weapons that the PCs get will have the appearance of being made of polished mother of pearl, so I'm optimistic that this will be interesting and memorable.
Clearly this idea is at a low level of refinement and I can use all the help I can get.