Cystrisen

An integral part of the reincarnation cycle of Elanni and Gardener is the gathering of righteousness and the eradication of evil. When an Elanni dies their soul takes refuge in the Sea of Blood, there to await their rebirth. Their acts in life, both evil and good, follow them. Acts of altruism, temperance, kind endurance and the like empower the Gardener to continue its own cycle of rebirth and assist the Elanni when the time comes for them to re-enter the world. Selfishness, spite, hatred and every kind of evil are gathered like poison from the bloodstream and expelled onto the Gardener's satellites, where to be permanently destroyed it must be purified by Elanni hands. Evil forced into the Material Realm in this fashion takes the form of a Cystrisen, bubbling up on the shores of the Sea of Blood and bursting forth in the shape of a lesser monster.
These monsters almost always have plague-like characteristics; though predators by nature, they reproduce rapidly and expand their territories without ceasing. Rarely do they possess anything beyond rudimentary intelligence, though there are exceptions. In order to rid the world of one of these monsters for good, killing alone is insufficient. The evil that formed them must be purified through ritual blessing. This most often takes the form of an invocation of a particular Guardian's blessing. Failing to deal with a Cystrisen in this fashion only makes it worse. The evil spirit will regenerate a body for itself and return stronger and - most distressingly - with memory. A creature with many regenerations becomes a dangerous threat indeed that will hunt down its slayers with hateful persistence.
Though Cystrisen are not part of any natural ecosystem and therefore have no specific natural predators, they do fall prey to another class of monsters: the Karrusk.