Creature: TU-Rats

Two foot high ratlings, humanoid, dressed in simple leather and cloth garments and carrying needle knives (sometimes poisoned) and tiny bows and slings. They are primitive by some measures, but civilised, living (typically) in large nest communities. Teams of TU-Rats have been known to ride pack-horses and other large domesticated animals. Unlike other rats and ratlings they have long outgrown scavenging as a way of life.

Oh, and TU stands for Telepathically United.

The cranium of a TU-Rat is slightly larger than might be expected for a bipedal rat of their overall size. They create an open psychic field to other TU-Rats. They are individuals but share and coordinate via a groupthink as situations require. A TU-Rat is always aware of every other TU-Rat within 50 feet, and can transmit to TU-Rats much further away by a mental relay effect: messages are passed on but are not instantaneous.

TU-Rats trade with other intelligent races sometimes. They are not aggressive generally, but can be territorial. A TU-Rat by itself will not be a great challenge for a party of adventurers if they have to kill it. Problems occur when dealing with large groups of TU-Rats that attack en masse and which can overcome even the most hardy of warriors. The TU-Rat psychic field can have an effect on humans and other races.