Cybermat

The Cybermen used small cybernetic creatures called Cybermats as advance guards and as attack carriers of plagues. The Cybermats originated on Mondas during the earliest phases of Cyberman history, when most of the planet had not yet converted. (BFA: Spare Parts)

Cybermats tended to resemble oversized metallic silver fish and have segmented bodies with cilia-like tactile sensor probes along the base of their heads.

The Cyber-tombs on Telos had tunnels for the Cybermats to move out through from the tombs into the main control rooms. (DW: The Tomb of the Cybermen)

Cybermats were created by Cybermen using bodies (or parts of bodies) of humanoids not suitible for Cyber-conversion; very young children or babies. (BFBS: The Crystal of Cantus)

Weaknesses
Cybermats shared the Cyberman's weakness for gold. (DW: Revenge of the Cybermen) They could also be disabled with electric charges. (DW: The Tomb of the Cybermen)

Variants

 * From early in the Cyberman's history before they froze themselves on Telos, these variants had crystalline eyes and antennae through which they receive commands. (DW: The Tomb of the Cybermen)


 * In the 21st century when the Cybermen attempted to infiltrate Space Station W3 they had photoreceptors for eyes rather than crystaline based eyes. (DW: The Wheel in Space)


 * When the Cybermen infiltrated Nerva Beacon in a plot to destroy Voga the Cybermats had segmented, eyeless, flat bodies without cilia. (DW: Revenge of the Cybermen)