Editing TROS in the Hammer:Magic Spirits (section)

==Ambient Power==
There is a limit to the amount of power/energy that can be draw upon in any one physical area, called the ambient power.  The ambient power is measured in dice, and is usually around 30 for any given area.  The ambient power replenishes at the same rate (1 per two hours) as the spirits Power Pool.  Whenever a spirit draws power (using the Mana effects) they draw down this ambient power.  If a number of spirits are operating at the same time, the ambient power can dissappear very quickly.