If a patch of mold has sprung up in your cel­lar, you’d best inves­ti­gate.

Check the con­sis­ten­cy: If it’s black, brown, green, or at all fuzzy, you’re fine—scrub it off; don’t wor­ry about it again. If it’s pus-yel­low, stroked with grey veins and start­ing the ends of slimy, wig­gling fla­gel­la, you may be in a spot of trou­ble.

Scrape off the mold and see what’s under­neath. There’ll be more of it under­neath, sad­ly. It’ll have eat­en all the way through the mor­tar of the cel­lar wall. See that tun­nel, that mycelial ori­fice? Alas: An out­growth of the Shim­mel­ing, the Mold Between Worlds, has reached its sticky fin­gers into your base­ment.

Get an axe or a sledge­ham­mer. Bash down that bit of the wall. Pull the wreck­age away, mind­ing the yel­low-green goo, and sur­vey what lies beyond. A great sphinc­ter of sorts. Yel­low-grey, slimy, smelling of bleach. Sort of a round, fleshy mold-door right inside your home.

At this point, you’ve a choice. Either douse the thing in kerosene and light it on fire, or crawl inside it. Pre­sum­ing you take the lat­ter option, go ahead and squeeze in. Go elbows-first, so you can pry the sticky sphinc­ter open. Wrig­gle inside. Take note of how imme­di­ate­ly slip­pery-slimy you get. (You weren’t too fond of those clothes?) Keep shim­my­ing. The going will be dark, but there’ll be light at the end. Even­tu­al­ly, you’ll find your way into some sort of stom­ach, a cham­ber with lots of oth­er tubes feed­ing off of it. There’ll be slime up to your waist. Note how it tin­gles.

There will be lit­tle nod­ules hang­ing by ten­drils from the ceil­ing, like gross fruit. These nod­ules glow, giv­ing off just enough light to reveal that the stom­ach-cham­ber is lined with count­less tiny, wig­gling fla­gel­la. If you stand still for too long, these fla­gel­la will attach them­selves to your flesh and suck it gen­tly.

Make sure not to stand around too long, lest the fla­gel­la suck you dry of juices. Keep squeez­ing through the slimy jel­ly-depths of the Shim­mel­ing. (You’ll most like­ly be used to the smell, by now.) Fol­low the pur­ple veins (the big ones.) Avoid the sym­bionts (they’ll liq­uidize you.) Fol­low them all the way to the heart.

The heart will be one of many, an oozy clod of pur­ple myceli­um, throb­bing with puls­es of weird ichor. Still have that axe? Good. Give the heart a cou­ple of good, sound whacks. Note how the beast reacts: it’ll begin to shud­der and con­tract. The walls will squeeze you. Fla­gel­la will start to spew some sort of yolk-like lubri­cant. You’ll be squeezed out of the heart-cham­ber, pro­pelled by the gushy peri­stal­sis of the Shim­mel­ing’s flight instinct. Hold your breath, now: the trip may be long.

You’ll be vom­it­ed out into your cel­lar, extrud­ed from the guts. Get up. Notice how the moldy sphinc­ter-thing has retract­ed after eject­ing you? You’ve chased it off. Board up the hole in your wall, and hope the Shim­mel­ing nev­er braves your cel­lar again.

Note: Yours was a best-case sce­nario.

The Shimmeling

In the vast and alien reach­es between words creep the oozy fin­gers of the Shim­mel­ing: A fun­gal organ­ism of incon­ceiv­able size and end­less hunger. It push­es its slow arms through leagues of soil and stone and space­time, con­sum­ing every iota of nutri­tion. It dis­places square kilo­me­ters of stone, grad­u­al­ly fill­ing its path with the twist­ed pas­sages, sac­cu­lat­ed halls, and cav­ernous cham­bers of its own slimy giz­zards. It is a beast of unknow­able size, dri­ven by some slow and hun­gry intel­li­gence.

The Shim­mel­ing’s mas­sive guts are an ecosys­tem pop­u­lat­ed and main­tained by a mul­ti­tude of sym­biont species. Among them are:

1. So-called leuko­cytes. March­ing, mil­i­tant, ready to reduce your cells to sticky nutri­ent goo with gouts of caus­tic lysis-juice.
2. Spiny salt-eaters with slick, exten­sile arms, like jel­ly­fish, grop­ing end­less­ly, mind­less­ly for exposed flesh, eager to suck the nutri­ent salts from your very pores.
3. Wrig­gly, docile, haus­tric grubs that aid the Mold in its diges­tion. They are most­ly harm­less, but they are every­where, and you can nev­er sleep near­by them, for they will wrig­gle into your lungs, lured by the car­bon diox­ide of your exha­la­tions.
4. Var­ied, hor­ri­ble species of chthon­ic worms—trans­plants from the Under­world—wrig­gle freely in the Shim­mel­ing’s slip­pery giz­zard tubes, lead­ing an easy, par­a­sitic exis­tence.

Oth­er, more intel­li­gent crea­tures can be found with­in the Shim­mel­ing. Not inhab­i­tants, but trav­el­ers.

Though space and direc­tion have lit­tle bear­ing in the inter­stices between worlds, they are per­fect­ly sound with­in the tubes of the Shim­mel­ing. A trav­el­er may trek the slimy inte­ri­or of the mold, the innards of which are akin to fleshy, rugose, fun­gal caves. Ample (bleach scent­ed) air is present in these tubes, and the diges­tive slime, though caus­tic, is slow act­ing (its action upon the skin yields mere­ly a tin­gle.)

The Shim­mel­ing’s most notable prop­er­ty is its abil­i­ty to cre­ate reli­able gates between the Coast and oth­er worlds—most com­mon­ly the Under­world. These are not con­ve­nient gates, mind, giv­en that they appear seem­ing­ly semi-ran­dom­ly, accord­ing to unknown, pre­sum­ably spe­cif­ic con­di­tions, and are main­tained only in accor­dance with the Shim­mel­ing’s unknow­able appetites; not to men­tion that tra­vers­ing them is a nigh-unsur­viv­able trek through legions of mil­i­tant sym­biotes and leagues of organ-like, tox­ic climes.

Shim­mel­ing van­guard probes are apt to emerge in the sub­ter­ranean spaces of the World, estab­lish­ing “salients” where the tak­ing is good. In stag­nant, dead areas, devoid of nutri­tion, the mold will cease its advances (though the sym­biont crea­tures spilled from with­in its guts may not.) In areas rich with food (cel­lars, fun­gal caves,) the Shim­mel­ing will expand its salient, tak­ing on eli­gi­ble life as sym­biont species and con­sum­ing all avail­able fuel. The salient expands until it exhausts avail­able nutri­tion, or until it encoun­ters sun­light. The grey, wet ten­drils of the giant mold can­not abide sun­light, and (for­tu­nate­ly for the peo­ple of the coast) nev­er ven­ture above ground.

Author’s Note

Updat­ed mod­er­ate­ly for the release of Inter­nal Growth.