Eyes of Nurgle

Flies are vermin of Nurgle, as nearly everyone knows. They feast on rot and excrement, laying their eggs everywhere. What begins as a single green fly alighting somewhere nearby swiftly becomes dozens, hundreds. The swarm crawls over everything, into and out of the mouths of oblivious people around the magic user. Although they may seem like normal flies, a closer look reveals the bloated green bodies are fitted with minuscule wailing Human heads mounted on the insect body.

Also Known As: The Bleak Swarm, Grim Feastings, Legion

Attracted By: Dark Magic, Amethyst or Jade Magic, Magic of Nurgle

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption pg. 209