All species die. There are no exceptions. Other species should never have been born, and have only crossed over into our world as Neverspawn from the bosom of the Progenitor. When such species are reduced to a lone surviving individual, or a small isolated population, the Winnower often dispatches its most feared hunter to consume not only such beings' flesh, but the memory of their very existence.
The Eater Of Last Things is a predatory spirit monster that specializes in cleansing the world of cryptozoans, mythical creatures, and, on occasion, Progenitor cults who wish to create, protect, or summon such animals. It cares little for the moral disposition of its prey, and will happily consume either the last noble unicorn or the only remaining vile manticore. The Eater's only agenda is to hunt and eat the final specimens of a given species. If it successfully does so, that species will not only disappear from physical existence, but from the world's memory, as well. Thus, they will no longer have a presence in the Lingering World, either. It will be as though they had never existed.
When its full form can be seen clearly, the Eater Of Last Things looks like nothing so much as a bizarre hybrid of ape and toad, with features of other species on display as well. It has a roughly bipedal appearance, and moves about somewhat like an ape walking on its hind legs. Its head is like that of a gigantic toad, it has two powerful tentacles in place of forelimbs, a great fan-like fin runs the length of its spine, and its body is covered in thick, reddish black hair. Its independently focusable, chameleon-like eyes can extend from their sockets on wiry stalks, giving it a fuller range of vision and making it much harder to surprise.
However, the Eater's true form is rarely seen by anyone in the physical world. Because it exists mostly in the Lingering World, the Eater is usually encountered as a blurry, ghost-like form, and only crosses the Membrane fully when it is about to attack its targeted prey.
As far as can be determined, the creature is immortal, embodying as it does the will of natural selection itself. Luckily, though, it can be defeated for a time, and there are persistent rumors of hidden magic that allow users to either control the Eater for their own ends, or make themselves invisible to it and its master, the god-thing known as the Winnower. Of course, no one has ever verified these rumors...
The Eater's primary motivation is eternal hunger, and once it has scented its targeted prey, it will always attack her first in any round of combat. When this is not possible, the Eater will always target the weakest, most-poorly armored of its opponents first.
(NOTE: The Eater Of Last Things was designed for the Creepy Crawlies campaign scheme, but it can be used in any setting where magic and the occult are real. It was designed, in part, using the Random Esoteric Creature Generator for Classic Fantasy Role-Playing Games and their Modern Simulacra by James Raggi IV.)
Armor Class: 2
Attacks: 1 bite (1d7), 2 tentacles (1d5, constriction)
Move: 160 ft. (80 ft.); Swim 90 ft. (30 ft.)
Saves as: Warrior
Special: Devastating Bite, Eye Stalks, Odor, Out Of Phase, Resurrection, Rubbery Flesh, Swallow Whole, +4 on all saves, +1 on all attack rolls
Total Levels (Hit Dice): 8
Threat: Heroic (-6)
Traits: Brachiation, Constriction (2 tentacle attacks), Low-Light Vision, Pounce, Scent, Ultravision
Devastating Bite: The Eater's normal bite attack is deadly enough (1d7 hp), but it can double its potential damage to 2d7 on a critical success (i.e., a natural 20).
Eye Stalks: The Eater Of Last Things can extend its eyes from their sockets on long, wiry stalks 3 feet in length, which it can rotate a full 360 degrees, for maximum field of vision. While in this state, it can only be surprised on a result of 1 on a 1d5 surprise roll.
Odor: The Eater Of Last Things has a powerful, distinct, gut-wrenching scent of imminent death clinging to it wherever it goes. This foul stench can be detected even by animals who do not have the Scent ability, and reduces the Eater's chances of surprising its foes (it gets a -4 penalty on surprise checks). However, this odor also instills fear in its enemies; anyone smelling the Eater in the vicinity must make a save vs. paralysis against the Eater's Threat rating, or be forced to behave as though she lost a non-lethal conflict.
Out Of Phase: Though it can interact with the physical plane, the Eater Of Last Things exists mostly in The Lingering World, giving it a "blurry" appearance to most observers who are not also in The Lingering World. As a result, the first attack by any opponent on the physical plane against the Eater automatically fails. This benefit is negated if the Eater crosses the Membrane into our world (such as when it is about to attack its targeted prey), or if its opponent is in the Lingering World with it.
Resurrection: As an agent of The Winnower, the Eater Of Last Things cannot be permanently killed. If it is reduced to 0 or fewer hit points, it dissolves into a pool of slime and vaporizes, only to re-form itself completely restored to full hit points at some later time. The interval between the Eater's defeat and its reconstitution is best left to the BM, as suited to the needs of her story. However, the interval should be at least long enough for PCs to heal themselves and relish some small sense of victory.
Rubbery Flesh: The Eater Of Last Things has a resilient anatomy, such that it suffers no damage from any non-magical physical attack that inflicts less than half its natural maximum potential damage (for instance, if an attack form inflicts 1d12 hp, any attack roll that comes up less than 6 does 0 hp to the Eater, instead). Such attacks merely "bounce" off its flesh with no effect. Magical enhancements to attacks still inflict their bonus as damage, however (thus, a +3 claw attack would always inflict at least 3 hp damage).
Swallow Whole (Fast): The Eater Of Last Things can attempt to swallow alive any opponent it has grappled with its sticky tongue. If this opponent is its target prey, Size category does not matter. If the opponent is some other creature, she must be Size Small or smaller for the Eater to attempt this attack. First, the Eater must successfully strike its target with its frog-like tongue and initiate a Wrestle attempt; this attack form has a range of 20 ft. If the Wrestle attempt is successful, the Eater may swallow its prey whole. A swallowed creature takes 1d7 hp damage per round, and remains under the effects of the successful Wrestle the entire time; however, the Eater does not, and can continue to fight other opponents normally.
A swallowed creature can attempt to free itself by clawing, cutting, or otherwise ripping itself out of the Eater's gullet. This takes the form of a standard Tough save vs. paralysis, with further -5 penalty to the roll.