I just feel that these guys need a certain something to make them both surprisingly dangerous as well as fun. Whilst this might be fun for an encounter it seems like it might be less fun as a recurring feature (although repeated uses is probably not fun for casters with an antimagic field so they should be able to recur only when there are other magic vulnerable enemies they are able to fight. I thought an interesting aspect of the fight might be to ensure that everyone was outside of the cube before it got destroyed. If you get eaten by the cube you are moved to a demiplane inside it where things are really wierd. I am also toying with the idea that they are a compact surface of a bigger cube in an extraplanar space.
So many cheap answers come from spells: walls, flying, misty step, summoned enemies, animated objects. I am thinking something like an antimagic field for a start. For an ooze to be a threat it needs a lot of love at this level.
Normally oozes are not such a big deal - slow, not much by way of ranged attacks, not so smart. Possibly in multiples but should represent a threat to a party that can cast wall of force as well as much higher level spells. I am talking a real challenge for a smart, optimised party of levels 11 to 13.
What would a high level ooze/gelatinous cube look like?
