These are all different names for what is basically the same thing. A group of mages all linked to a source of mana.
The most common source is a deity; all of that deity's priests and avatars will generally have a link to it. They can request mana at will, but whether or not the deity chooses to supply it depends how much the deity has available and how much they like the supplicant. For day-to-day things, there's generally an almost unlimited amount of mana available from a god. During emergencies, though (such as a war with a rival power), there may be so many people demanding mana that the deity has to carefully ration it... either only giving out tiny amounts or only answering the calls of its most important agents.
As a general rule, drawing power from the deity multiple times in the same day will often result in at least some cursory attention to determine whether or not you are being wasteful. Most deities know that emergencies happen and will not hesitate to supply someone in desperate straits, but a priest who gets into desperate straits repeatedly had better be on a mission for their deity.
Mages (generally speaking, the only serious difference between a mage and a priest is that the mage isn't subservient to their mana source) have seen the advantages of this and sometimes form their own mana pools. The members of the organization gather together and perform a ritual which unites them spiritually. Each one contributes a certain amount of mana to a great pool of energy that they can all draw upon in need. There's a lot of flexibility in how this gets set up... in some groups, new members are expected to have no access to the pool, but still have to contribute... only after they have been promoted in rank are they allowed to draw upon it.
A Mana Pool must be centered in a physical spot and thus is vulnerable to disruption or "theft" (tapping it without permission of the group). Theoretically, a Mana Pool could be embodied in a specific person, but it's a rare group willing to do that. This is usually attempted as part of trying to become a god; it usually just attracts enough real divine attention to get yourself killed quickly.
Posted by Kiz at November 14, 2004 12:25 PMCommentsPost a comment