Creature seed: The New Saxony Silk Rat.

Blame this.

the-new-saxony-silk-rat-rattus-sericum-google-docs

The New Saxony Silk Rat

(rattus sericum)

This species of domestic rat appears to have been cultivated for its wool for at least six thousand years.  It is somewhat larger than a Norwegian rat: feral specimens average about a foot and a half long, and about three pounds in weight (a fully-bred Silk Rat is a bit larger).  The species is fully domesticated, and make affectionate, intelligent, and loyal pets.  The wool of the Silk Rat can be gathered or sheared without harming the rat, and is particularly valuable for its uncanny resemblance to silk. Depending on the location, in fact, Silk Rat wool is either openly sold as a silk substitute, or it is passed off as actual silk. The species is typically kept in check by local predators; most carnivores find them tasty snacks.

Now, if you’ve never heard of the Silk Rat, don’t be upset. It merely means that there are no immediately accessible interdimensional portals in your home dimension.  The New Saxony Silk Rat is an invasive species par excellence: if there’s any kind of interdimensional portal in the area that operates on anything like a regular schedule, then eventually a viable Silk Rat breeding population will import itself. Note that New Saxony (a bustling imperial republic on one particular timeline) is not the original location of this species, but merely the first place where the Silk Rat was encountered by your campaign’s relevant authorities. The home universe of Silk Rats remains unknown.

There’s nothing obviously supernatural about the Silk Rat’s ability to establish itself, by the way.  You can keep the species from crossing over… if you use clean room protocols and forbid any kind of cargo transfer in either direction. But if it’s anything more than that then Silk Rats will prove to be even better at establishing itself in a new environment than black or Norwegian rats are.  It’s almost as if the species can detect dimensional portals, and have a biological urge to go near them.  Indeed, some researchers claim that that is exactly what is happening, but nobody’s been able to prove it one way or the other.

In practical terms all of this means that sufficiently dedicated researchers with access to local records can often trace the approximate location of a dimensional portal by tracking the spread of Silk Rats in that particular dimension. As the species has genuine domestic value, humans typically encourage their breeding, which means that there’s usually a trail of some kind leading back to the general location where Silk Rats first appeared.  Unfortunately, this same inherent value means that culling all the Silk Rat colonies on a particular alternate timeline — once those colonies have been established, and noted by the locals — will merely confirm to an outside observer that there is regular, and secretive, paratime travel going on in that particular timeline. And you’d have to keep doing the culling, too, given that the New Saxony Silk Rat is just at good at reestablishing a breeding colony as the species is at establishing one.

Oh, and to answer the inevitable question: they taste like rats.  Nothing special, if you like that sort of thing. Maybe a little tough.