The Casket Guards and Liche Priest/Liche High Priest associated with the Casket act much like a war machine's crew for the Casket of Souls. The Casket of Souls uses the rules for war machines, with the following exceptions:

If, for whatever reason, there is no Liche Priest or Liche High Priest acting as part of the crew for the Casket at the beginning of any Tomb Kings turn, the Casket and its two Casket Guards immediately collapse and are removed from the table.

The Casket of Souls cannot move.

Any hits from shooting that strike the Casket itself are ignored. Hits on the crew are randomised between the Casket's two Guards and any associated Liche Priests or Liche High Priests.