true monsters

True Monsters are unique creatures in Scarterra or Scaraqua.
In colloquial modern English the definition of monster has evolved to refer to anyone or anything whose behavior is frightening and dangerous. Originally, the definition was essentially simply a unique aberration.
The etymology of "demonstration" is that you "de-monster" by showing the thing or event is repeatable.
Comparing Greek mythology to most fantasy settings, a lot of fantasy worlds have a creature type known as medusas. You might have a coven or pack of medusas, plural, but Greek mythology just had one person named Medusa. Likewise, they had the Minotaur, not a minotaur or a race of Minotaurs.

Causes

True Monsters come from all sorts of origins in Scarterra, Scaraqua, and Scarnoctis.
All of the Nine have at least a few powerful spirits that are truly unique and thus technically True Monsters. Examples include the Shadow Creeper and the Manticore. As an added bonus, if they are slain, they can be ressurected relatively easily.
Many Fair Folk are part of a kith but many are not and some are unique enough to be True Monsters, at least as far mortals know. Qalupalika certainly qualifies. Fae Remnants are even more likely to qualify as True Monsters.
Some necromancers make it a personal undead True Monsters. Unusual confluences of magical energy combined with unusual deaths can sometimes create some unique exogenic undead that qualify as True Monsters.
Sometimes the Nine deliberately create a True Monster in the mortal plane either as a pawn or a punishment. Greymoria is the most likely to do so, but she is not the only one. the Nine are not infallible with their power. Sometimes they can accidentally create a True Monster.
Occasionally, magical forces cause creatures to mutate into True Monsters without any outside force deliberately pushing that to happen. This is especially likely to happen in Scarnoctis.

Authors Note

As a lover of inter cultural fantasy and mythology I have a kitchen sink approach to fantasy where I like to include a bit of everything.
That said, I like for things to be internally consistent. If I want to create a race of fantasy beasts, I need to make sure they are have enough space with enough food to maintain a viable breeding population and they need to be strong enough to defend themselves against the other creatures already in their habitat but not so strong that they destroy everything they come across.
Introducing True Monsters, makes realism and consistency easier because I only have to make room for one representative of something.

Type

Supernatural

Rarity

Rare