Cleon
Legend
What if we advance an aballin to 13HD? I'd like to see the comparison to the advanced cube.
As far as the drowning, etc, I'd go with imp grab and then an adapted version of the aballin's drown (minus the stuff that goes into imp grab). Since these are so similar to aballins, I think it's good to keep the mechanics similar also. We might also be able to something with the changing consistency bit.
I've got a copy of Monsters of Faerun, but it's buried somewhere in my collection and would be difficult to find, so would someone else care to do the comparison?
Both the Aballin and Living Pool monsters strongly remind me of a creature from John Norman's Nomads of Gor - there's a good description of it on this webpage under "Yellow Pool of Turia". Since the book was published in 1969, it's possible it actually inspired one or both of these monsters. I certainly remember thinking I could steal the idea after reading the book.