The tingler was a nasty little device used by the Phyrexians during their invasion of Dominaria. Tinglers resembled spined centipede-like insects. One end of the tingler was fashioned with small hooks used both for movement and for carrying out its main function, which was to zombify enemy troops in the midst of battle, turning them against their allies.
The tingler zombifies its victims by crawling into the mouth and using its hooks to literally rip out the spinal cord, effectively killing the host. It would then crawl down the mouth and into the cavity once occupied by the spine and replace the spinal cord, controlling the victim's body.
The card Spinal Embrace represents the tingler, and the cards Metathran Zombie, Vodalian Zombie, and Shivan Zombie are examples of "tingled" victims, as told by the tingler's trademark "mouthpeice" and the metallic spines protruding from their backs.