Linked Emitting (Magic/Mental) Interplanar Navigation Guidance System
(L.E.M.M.I.N.G.S.)
Ten million million possible alternate dimensions that the first Pathfinder teams could have accessed, and they manage to find one where at least some of the locals could laugh at the acronym. What are the odds, huh? …Don’t actually try to calculate the odds. The Pathfinders get oddly superstitious about anything that looks like it might be magic, and amateur statistical analysis is high up on the list. At the absolute minimum you’re supposed to ground yourself first.
LEMMINGS, unsurprisingly, look a lot like ordinary, regular lemmings: the Pathfinders’ home universe have modified LEMMINGS to have bright orange fur and make them a bit larger, but that’s just to make them easier to see and find. They reproduce normally among themselves; breeding LEMMINGS to regular lemmings gets sterile LEMMINGS, but a competent veterinary mage can fix that problem without too much difficulty. LEMMINGS are also noticeably more docile and tame around humans: they don’t exactly make for good pets, but they’re generally inoffensive. Lifespan is irrelevant, as competent veterinary mages can also keep small rodents from dying of old age indefinitely.
The Pathfinders use LEMMINGS as biological sensor/communication devices: LEMMINGS can detect the small, localized holes in spacetime that can be used to travel from one universe to the other. And, as all LEMMINGS are magically linked to each other, where one goes the others can soon follow. The diffusion of knowledge is not instantaneous, for reasons unknown even to the Pathfinders’ home civilization — but it’s reasonably fast, and transcends dimensions. A side effect of this is that simple messages can be passed along the network, if you don’t mind everybody on that network getting it: LEMMINGS transmit the message via precise bites into the nearest piece of softwood.
Note, by the way, that the Pathfinders’ home culture and universe has been carefully left undefined. It’s definitely magical, and obviously capable of sending out organized exploration teams; but other than that it could be anything from a malevolent expansionistic empire to a benevolent mutual aid society. Although making it, say, a benevolent expansionistic empire might be interesting, too…