Slithering through dreams (Snake Isekai ?)

Mana poisoning - One of the most common ailments of alchemists, mages, and those that work with rich mana sources. Most people tend to instinctively avoid places with mana concentrations high enough to be dangerous to normal living. Unfortunately, some humans are born with a weird disease of the soul, known as “curiosity” or “love of magic”, or, worst of all “call to adventure”. All of that, usually ends with you, in a ditch somewhere, with a gigantic wound- a gift from some passing creature. 

Suddenly instead of your organs being filled with air, they are filled with water! Or fire! Or electricity! Remember, be calm! If you know mana manipulation- try to expel it. Block the wound with magical resistant cloth! Put pressure above the wound to stop the circulation of blood (or if you are eldritch- liquid agony). If you did all of that, your chances of survival are high 25%! Just remember to get yourself checked in a clinic when you come back.

And then one of your friends, in panic, throws mana potion at the wound instead of a healing one! SURPRISE! Mana poisoning becomes manafication! Now you have two options- you find a way to evolve into a pure mana being… Or your organs and skin start becoming mana objects, eventually, suddenly, falling through your body. But don’t worry! It will live on, as a precious material for experiments of the Magical college! They will even leave a plaque with your name next to the sample name… if they find a graduate student to do that.

 Spirited-cave snakes - It’s a ghost! It’s a snake! No, it’s a spirited cave snake! Aan ambush specialised subspecies of snake. After increasing hiding skills to their absolute peaks, and living a life full of death… a snake becomes something more.. Or something less than a living being.

While extremely dangerous, many of their skills require a lot of planning and preparation. Many earth and stone magic based traps, or just improved hiding spots.They tend to live in caves