Cranio-necrotizers were small hand held devices used by the Wardens.

They had two uses; for small scale production and distribution of Warden nanites to spread the Warden presence, and as communications devices. Each cranio-necrotizer was linked by a subspace signal functioning much the same as Borg Central plexus' or Interplexing beacons, they could indeed be linked technologies given the Borg origins of the Wardens. (Away Team video game: )