I think this figure dates from the early 1980's, when Grenadier had the franchise for TSR's AD&D game - I think they held this between 1980 and 1983. The figure itself is similar in style to the illustrations used in the AD&D 2nd edition "Monster Manual":
I had my doubts when I started this figure - the styling is quite naive (but then most of the Grenadier figures from that date were), and the main "body" of the figure is actually lopsided. I'm guessing this was to try and give the impression of the figure still forming from mist. I'm quite pleased with the way it turned out - with the use of inks and a bit of drybrushing, I think it came out quite well. I'm especially pleased with the terracotta jar it is escaping from! The tiles on the base are Milliput, and conceal the original Grenadier base.