D&D Monsters: Umber Hulks

The origins of the D&D umber hulk are not clear. It predates what we'd now call 1E, first appearing in the Greyhawk supplement, and it has been proposed that it may be based on one of the same set of plastic toys that inspired the owlbear, rust monster, and bulette. If so, it doesn't closely resemble any of them, while the other three are very clearly drawn to resemble the toys in the 1E Monster Manual. So, if it's inspired by them at all, the connection is still vague enough that, to all intents and purposes, it's an original creation. Certainly, its signature power is original, doubtless intended to be related to its unusual appearance and, while evil sorcerers might be able to do something similar in myth, the same is not generally true of monsters.

DW Monsters: Zygons

The fourth race on my list of the seven key humanoid ‘monster’ races are the shape-shifting Zygons.

Appearances

The Zygons have a slightly unusual history, compared with those I’ve dealt with so far. They first appear slightly later, during the fourth Doctor story Terror of the Zygons, but that’s not the oddity. They immediately stood out due to a distinctive design and a particularly well-respected debut story and after that they… well, they just didn’t appear again in the classic series. In fact, they didn’t appear on TV again for another 38 years, although they have now shown up as significant antagonists twice in the modern era.

D&D Monsters: Devils

In regular English, the term 'devil', when not applied specifically to Satan, is essentially synonymous with 'demon'. Whereas the word 'demon' originally had a more benign meaning, 'devil' has always meant an evil entity, and now typically means one that is specifically part of the Christian mythos even if the general concept exists in other religions, too. 

In D&D, however, devils are distinct from demons, making up the organised legions of Hell rather than being rampaging creatures of malevolent chaos. In 1E, six main types exist, although other common ones have been added since, all fitting within a defined hierarchy where weaker devils can (with difficulty) be promoted to higher ranks at the whims of those even higher up the chain. Compared with the demons, these six standard types are more likely to owe their origins to myth or at least to traditional depictions of such beings, rather than just being odd combinations of animal parts. 

D&D Monsters: Erinyes

The Erinyes originate in Greek myth, where they are goddesses of vengeance cursing kinslayers, oathbreakers, and the like; they are probably better known under their Roman name of "Furies". These original versions appeared as ugly women, typically with snakes entwined in their hair and wrapped around their bodies and limbs. Sometimes they had wings, sometimes not, and later depictions of them are similarly varied.

Some versions of the myths state that there are only three Erinyes, but others are much vaguer about the numbers. Notably, the three named Erinyes stand guard over the City of Dis surrounding the Sixth Circle of Hell in Dante's Inferno. It may be this that inspired their adoption as a type of "devil" in D&D, although they (and Dis) are moved to the Second Circle in the 1E Monster Manual, befitting their status as the weakest of the true devils in that edition. Something of a demotion from their mythic origins, then.