I worked on his design some more and I'm pretty happy with it ovo

He's made of goo with a sort of 'membrane' around the outside. He can change the shape of it at will but can't make himself larger or smaller without a supply of water, as his goo is made of a mix of that and an enzyme he makes.

While he usually has the tentacle hair and tail, this is just his personal choice. He can literally look like whatever he wants so long as he has enough mass to create it with.

When it's warm he has to take in water more often, otherwise he shrinks as it slowly evaporates. If he shrinks too much he starts to lose his ability to control his form and he becomes a much simpler looking organism, even getting to the point that he can only control his third eye.

This third eye has basic physic ability, but only enough to control his form and shape him. He can't levitate or anything like that. It open when he's over exerting himself to make it easier to move.

The last thing is he can harden this membrane into any shape he likes, which makes for many excellent sexy time possibilities ehehehe

EDIT: I should also note that he can alter his enzymes and chemicals to have specific effects on other creatures. Which, yes, does include aphrodisiacs.
And when he gets too cold his movement slows down as his goo starts freezing. It's possible for him to be completely solid and unmovable, but he'll thaw out and be fine again if warmed up.