Eldritchy Things adds (or intends to add) various mobs, items or silly occult artifacts inspired by common eldritch horror works like The King in Yellow or The Shadow over Innsmouth (or spooky stuff in general).

Currently, it only adds two mobs and one item, inspired by The King in Yellow (with more by the same work to come) and Sightstealers

Devoted
...are these gremlins, banished from regular illager societies due to their... interesting beliefs. They wield yellow daggers and will inflict the Madness Effect (Freezing, Converts Villagers into more Devoted).
They may occasionally drop their daggers, food for thought. Usually found within dark forests, or any biome that can spawn woodland mansions.

Rascal

...s are ambush predators that utilize invisibilty to catch their victims off guard.

Once a Rascal has spotted you, they'll immediately become invisble and start approaching, once they've gotten to a sizeable distance away from you, they will lose their invisiblity and strike. Upon reaching half health, Rascals will retreat and attempt to heal before coming back to annoy you, again. While one is vicious, they often work better in groups.

FAQ:
Why?

There are so many great mods that follow this theme (that also do it way better) like Miskatonic Mysteries or Beyond the Veil, but i've noticed that they aren't/won't be available for versions that i commonly play on (1.20.1 Forge). So, instead of yapping in the comments and begging for a port, i just decided to try my hand at making something similar. Also functioning as my first introduction to forge modding.

Fabric?

Nope (Currently). Mod is MIT and Source code is available, do it yourself :<

Credits:
Miskatonic Mysteries for being the Main inspiration to try my hand at something similar.
Beyond the veil is also one of the mods that is (by my decree) incredibly underrated, and also inspired me to make this.
Metus Oblita (by Skarrier) also had a huge impact on me when it came to finding the motivation to just pull up intellij and cook for a few hours.