Painted Tree Rat Callistomys pictus

A rodent from the state of Bahia, Brazil. The painted tree-rat is found in the Atlantic forest. It also occurs in cocoa plantations where some native trees remain. As far as known, it is nocturnal.

Endangered

Atlas Gundi Ctenodactylus gundi

This rodent is found in northern Africa on the south side of the Atlas Mountains in Algeria, Libya, Morocco, and Tunisia. It lives in rocky, arid places, making its home in crevices and under boulders. It forages for leaves, stems, flowers and seeds over large distances because of the scarcity of suitable plants. It does not drink, obtaining sufficient water from its diet.

A Brazilian guinea pig (Cavia aperea) with a pup in Sao Paolo, Brazil

The maned rat is a real shocker! Though it looks like they've been zapped, their electrifying hairdo is actually meant to resemble a porcupine. If that's not enough they have another trick up their sleeves: maned rats are the only rodent known to be poisonous! Maned rats will rub themselves against poison arrow trees to accumulate toxins, which makes a very poor treat for would-be predators.

Modern setting? Historical setting? Rats are common throughout history and throughout the world!

I said “urban fantasy” at first, and cities are where rats famously thrive—consider a many-bodied squirming creature in the shadows below the subway tracks, genius loci in all but name, for its single-bodied servants are eyes and ears throughout the city… But there can also be country rat kings, running their own little farm fiefdoms! Shipboard rat kings, blessing or cursing their sailors as they deserve! Roaming, terrible, plague-bearing rat kings, seeking only to spread and destroy…

Rat kings can develop naturally, due to sticky materials and/or an instinct to cling to one another for winter warmth. [wikipedia] More ominously, if perhaps only apocryphally (ie like all folklore), rat kings can be created, forced by human hands.

Rat kings as metaphor for the monstrous depths to which humans may sink in dire circumstances—or of the strength and power they may find in community, in those same dire circumstances! Rat kings as metaphors for assimilation, into cults or into cultures or under that insidious social pressure against “being weird”! Body horror rat kings! Rat kings who are wise elders pooling knowledge and cultural history! Rat kings as love, which may or may not be toxic; rat kings as the raging desire to tear each other to pieces but the knowledge that you will only survive through cooperation; rat kings as multi-voiced horrors or rat kings as comedically squabbling committees… Rat kings!