The Ghost Fish aren't how their name suggests a kind of spiritual entity, but a species of tiny, slimy, discoloured fish who enter animals through every bodily orifice. When they feel like they are being eaten (usually when they are touched at two or more Sides at the same time) they inflate themselves like a blowfisch (sadly they can't deflate and usually get stuck, but luckily they are omnivores so they can eat their 'predator'). Furthermore instead of eyes they have a round protusion filled with nerve-strings and pus on their head. If they inflate themselves the protusion Pops and the nerve-strings Fall Out. These nerve-strings are now used to slowly take over the Hosts body. As soon as they have control over most of the body they start seeking out other member of their Hosts race which they then either hug while increasing their strength or bodyslam until the others body is broken. When they are about todie they submerge their Host in water. As soon as they are dead they body Pops and sperm and eggcells are released causing the water to be infested with their kin. Sometimes a hybrid with the Hosts race is born (they can enter through the reproductive Organs) these hybrids are usually not able to sustain their life, thusly leading an often multiple days long suffering before death. Due to them looking like a baby of another race it is a perfect Bait.
Although they inprison their Hosts in their body, before eventually taking over the brain and essentialy killing them (what at that time is a salvation for most) they themselves aren't aware of the fact. This is because they were forcibly evolved by a mage for war. The original species is the Farewell-fish.