Slimes are a common enemy in role playing games, so common we don’t really think much about where slimes came from. Soul Sacrifice has back stories for many of the game’s enemies including these gooey monsters.
In Soul Sacrifice, you have to pay a price to fulfill a wish. No matter how much a human has lost in despair, they always have something left to offer. What remains even after all is lost is their body.
If a human’s desire is gold, their body would melt into a muddy soup, leaving just the bones behind. This semi-transparent soup, made from the body mixed with bones and organs, becomes a slimy mixture along with other parts that have transformed into jewels, money, and other materials the human wished for before dying.
Mankind’s greed is immeasurable, as having their own body no longer suffices. Slimes are born from many human desires, whether it’s gold or food. The slimes you see in this game are the typical appearances of humans who have fallen deep into their own desires.