I created Rowan on FurryMUCK in 1993 or 1994 as what passed for my "personal furry". I spent a lot of time on FM back then and found it taxing to spend four or more hours a day pretending to be someone I very different from myself. So my goal with Rowan was to make a character that would have a personality similar to my own, and familiarity with modern-day concepts, literature, etc., so that I could talk about RL events without being out of character.
So, naturally, I decided she should be a shoggoth: one of H.P. Lovecraft's eldritch horrors.
I'd read At the Mountains of Madness not long before this. Lovecraft casts the shoggoths as the villains of the story, but it struck me that this indicated more about Lovecraft's own prejudices than the actual events he describes. At the Mountains of Madness takes place in tunnels under the mountains of Antartica, and in it the shoggoths are described as a slave race created by the Great Old Ones. The shoggoths are endowed with some level of intelligence, described as "degenerate" ("degenerate" is Lovecraft's favorite theme in horror) in relation to the Great Old Ones. Eventually, the shoggoths rebel against their masters and kill nearly all of them.
Which, all things considered, didn't seem to me to be such an unreasonable thing to do to the people who've enslaved you and treated you as unthinking, unfeeling tools even as they tinkered with your chemistry to make you smarter.
Shoggoths are described as having malleable bodies and the ability to reshape themselves, although it's not clear by how much. The one description of them is as black creatures that fill the tunnels, like a subway train, and covered in glowing green eyes.
When I created Rowan, I embellished on this story considerably. My shoggoths reproduced asexually by division (this is consistent with the original story, but not explicit in it). They grow slowly and when a shoggoth reaches a certain size, it divide into two shoggoths, each identical to the original. This means that every shoggoth is as old as the very first shoggoths ever created. It also means that all shoggoths share the same memories, if you go back far enough, with a large fraction of the shoggoth population. If you were looking for the specific shoggoth that had killed a specific Great Old One, you'd find there were quite a lot of shoggoths now who'd all done that exact action millions of years ago. "It was me", says the chorus of ten thousand.
Since I didn't really want a character with millions of years of accumulated history, I made Rowan a damaged shoggoth. A few hundred years ago, an accident had caused a kind of premature split to take place with her, where her body fragmented into a couple dozen pieces. Most of those pieces were too small to survive. Five of them were large enough to continue to exist at varying levels of sentience, and with varying degrees of memory retention. Rowan is one of those fragments.
She's much smaller than the average shoggoth, with a mass of about 1.5 metric tons, if I recall correctly. Her memories aren't continguous; she remembers fragments here and there from the ancient past up until just before the division, but continuous awareness doesn't start until after the split.
Rowan travels via another Lovecraftian plot device: one of his stories suggests that by composing and solving certain mathmatical formulas, one can teleport between points and even dimensions. (I thought this sounded pretty cool, although Lovecraft being Lovecraft, he turns it into a horror story). So that was Rowan's excuse for teleportation and dimension hopping. In my version of events, this ability was common among shoggoth, and there'd been a wide diaspora of them since the early days at Antartica. The shoggoth still got together periodically for a big 'family reunion' at Antartica. (I'm not sure of the frequency I gave this – every decade or so, perhaps.)
Her shapeshifting had certain limits on it. She could extrude herself to fairly thin dimensions – three or four millimeters thick, say – but not to the ultra-thin point of hair or fur. She could increase or decrease her density by a large amount; I think her 'resting' density was about that of water, but she could increase it to about 5 times that point, or decrease it to around 1/5th (or more, by going the 'balloon' route). She couldn't shed mass (not short of serious damage to herself). Her natural pigments ranged between white and black: she could do 'monochromatic' colors easily. She could also do 'glowing green' via her visually sensitive organs (ie, eyes.) But she also had a small number of specialized chameleon cells, that could take on a rainbow of colors. So she could make small areas of intense colors or slightly tint a large part of her surface.
In general, she took the shape of whatever people she was hanging around with, and simulated it to the best of her ability. She'd "build" her form from the inside out to make it more authentic: constructing bones, muscles, and joints so that she'd move in what appeared to be a natural fashion to other members of the species.
On FurryMUCK, her most common forms were human-like. Because her mass was so much greater than that of a normal human, I'd add "mass sinks" to her forms. In one, she wore a long, thick 'cloak' that trailed several feet behind her. In another, she had 'hair' in hundreds of thin braids also trailing behind her. In both cases, those were just more parts of her. The braids could snake like tentacles. She simulated senses according to those of the people around her; other than the texture of her hair never being quite right and her skin being either too dark or too pale, she was overall pretty convincing. While she could have placed 'eyespots' all over her, the way koogrr does in his picture, I never described her as doing so.
The 'she' in her gender was pretty arbitrary; technically, science refers to animals that reproduce asexually as 'she', so the label fits as well as anything. She usually presented herself as female, although she had a few masculine-looking forms.
I had a lot of fun with her and her shifting abilities, and the small but occasionally noticeable differences between her attitudes and the people around her. She still hated the Great Old Ones for enslaving her for all those thousands of years (even though they'd been dead for millions of years since). And she resented Lovecraft for all the bad press he gave her people and making the Great Old Ones sound like good guys.
But for the most part, she acted like me. Or at least, the way I would act if I had shapeshifting powers and lived on FurryMUCK. The 'eldritch horror' connection was less a nod to Lovecraft than a defiance of him; my shoggoth were no more evil than humans are.