Lešij (Leshy)
Forest apparitions or spirits from Slavic folklore. Known for their diverse forms, they possess the ability to alter their size, shapeshift, and manipulate the wind. They enjoy pranks and sometimes abduct women and girls. Some legends claim they take the spirits of the deceased girls they ruin as wives. While ancient, higher-ranking entities may be revered as forest guardians and classified as elementals in the Clock Tower's taxonomy, the individual encountered in this story was of a lower or middle rank.

Summoned as a Caster spirit, it was granted a makeshift Saint Graph composed of shadows and was patrolling the perimeter when it encountered Berserker. Mistaking Berserker for a mere human, it was obliterated with a single swing of an axe. It should be noted that it did not lack the ability to sense magical energy. In fact, it was rather skilled in this regard...

Fate:Lost Einherjar - Aslaug of the Aurora Volume 1 - Mythical Creature Encyclopedia - Compendium of Arcane Beings: Lešij (Leshy)