The ratatosk can enter into a contract to serve another creature as a familiar, forming a telepathic bond with its willing master. While the two are bonded, the master can sense what the ratatosk senses as long as they are within 1 mile of each other. While the ratatosk is within 10 feet of its master, the master shares the ratatosk's Magic Resistance trait. If its master violates the terms of the contract, the ratatosk can end its service as a familiar, ending the telepathic bond.