Many people on Reddit have been curious about especially why do I cross-post from other subs interesting videos of magical and pre-historic nature stuff. Even though I wrote this helpful explainer about things, people still want to know more. So here is a bit more on magic and the Hypogeum.
The term hypogeum, generically speaking comes from Greek, and means below (hypo, like hypothermia) earth (geum, like geo-caching). Subterranean or underground. Such natural, man-made, or augmented below-ground structures have persisted throughout human history since pre-historic times. There is one especially well known hypogeum, the Ħal Saflieni Hypogeum in Malta. (The history & pre-history of Malta, and other Mediterranean islands are especially fascinating on their own.)
While those historic hypogea have much in common with these types of physical structures, the classical Quatrian conception of the Hypogeum encompasses what in other cultures have been called the Underworld or the Otherworld.
As Wikipedia explains about this global mythological phenomenon:
Comparable religious, mythological or metaphysical concepts, such as a realm of supernatural beings and a realm of the dead, are found in cultures throughout the world. Spirits are thought to travel between worlds, or layers of existence in such traditions, usually along an axis such as a giant tree, a tent pole, a river, a rope or mountains.
Thus, in what is known to us about Quatrian myth, the Otherworld that is the Hypogeum may be accessed via a physical hypogeic structure such as a basement, a catacomb, a burial mound, a cave, or even a closet. The Hypogeum is neither good, nor evil, but encompasses both; all Powers are present in the vastness of the Hypogeum.
The nature of the Hypogeum in Quatrian myth, however, is not as a Land of the Dead, as modern audiences might think of such a thing today. It was instead a place of vibrancy, regeneration, and magic. Something perhaps akin to the magical cauldron of Celtic lore.
The Hypogeum in Quatrian lore is populated by all manner of magical beings, who have truck with our world, and have throughout all of time. Hypogeans have visited Earth endlessly, traversing easily the worlds while the passageways between them have remained open.
The Hypogeum is thus home to an endless array of Monsters & Magicians, including theriomorphic and therianthropic varieties of each. The struggle between these two sometimes collaborating and sometimes opposing forces is represented meta-symbolically in the Quatrian Winter Solstice Festival of the Hypogeum. (archived)
Thus, when I post things on Reddit which have weird or unusual animals in them, it is in recognition of Quatrian myth which says that magicians and monsters can take many forms when they cross over from the Hypogeum into our world. To be on the lookout for them. And that they often choose animal biomorphs, either because it suits their essential magical nature, or because they see the human form as too corrupt to want to take on. (Though some still choose to, for a variety of reasons.)