All of the info I have on the set, as well as the photos, come from Little Weirdos, a cool site focusing on mini monster figures.
We don’t know when they were first produced. I suspect they were a response to the popularity of Bakshi’s The Lord of the Rings and D&D, which would put them around ’79/’80, same as the Space Raiders and Space Creatures figures.
Does anyone remember them? Is the Medusa wearing a bra?
2 Warps to Neptune 
Haha, I had a lot of these. I would use my money for the book fair on erasers. So funny.
Book fairs! Totally forgot about that…
I love this toy-line, but there’s a major unexplained mystery regarding it: the NAME of this toy-line. I think that “mythological creatures” is simply LittleWeirdos describing the nature of the sculpts, rather than the actual name of the the toy-line. I’ve seen them referred to by similar descriptions, such as “myth monsters”. I’ve never once seen a one of these figures in it’s original packaging, nor even a photograph of that packaging. If anyone knows what they’re actually called, please let me know.
Although this group doesn’t yet contain any information about this toy-line, it does contain several other photographs of these figures: https://www.flickr.com/groups/diener/
I haven’t seen any in package either, and I have a pretty big collection of Diener packaging at this point. I’ll let you know if I find anything.
Please do. I’m very curious to know the actual name of this toy-line (and somewhat curious to know what year(s) they were released, as well).
Speaking of Diener packaging, the pride of my Diener collection is two McDonald’s Happy Meal boxes from the Space Creatures promotion.
And jumping back to this “mythological creatures” line, there are at least two variants: soft rubbery figures and rigid plastic figures. I assume that the rigid figures are later reissues, although I freely admit that this is nothing more than an educated guess.
Any updates regarding the name and/or packaging of this toy line, 2W2N?