The amount of spirits that can be created by The Undead Queen is only limited by the amount of chapter dice, there could be 4 spirits in play technically!

When a player is MARKED FOR DEATH (Adventure pack 1: Cult of the Death Knight) and their cult die is added to the row of chapter dice, think of it as becoming another fully black chapter dice. So it is included when having to roll pairs for spirits.

If using the death dice (found in the Collectors Box), when they are removed, roll a NORMAL chapter dice to add to the spirit pool.