The Witch Doctor will gladly come to serve any Underlord who chooses to build a Spirit Chamber. Within lie all the necessary tools for him to impart upon your minions the skills of the recently deceased, increasing their skill in battle at a remarkable rate.
In the Spirit Chamber, a Witch Doctor can enhance your minions by increasing their XP in a small amount of time. Thus increasing the combat level of your minions. This process costs quite some mana and gold. However, a Spirit can be used. If a creature is tortured to death in the Torture Chamber, they will become a Spirit. The Witch Doctor can then use this Spirit to give experience to another friendly creature. The Spirit that is used in this way will be consumed in the process.