|Image from Wikipedia|
Because of a comment Gustie left on my Sorcerer Patrol post, I’ve been playing Dragon Age: Origins recently. The magic system in this game uses the “mana” magic point system that has become standard in most computer RPGs. Spells are divided into activated and sustained categories. Activated spells cost a fixed amount of mana and have an immediate effect (which also may sometimes persist for a short period of time, but wears off quickly). Something like paralyze (which affects an enemy) is an activated effect, as is fireball.
Sustained spells, however, are essentially permanent but also reserve a fixed amount of mana which can’t be used for other magic while the sustained ability is maintained. Effects generated by this type of spell are often defensive (arcane shield, rock armor), but also auras which penalize opponents (miasma) or benefit allies (flaming weapons).
It occurs to me that this mechanism could be used for spells in a tabletop game as well, replacing or in addition to the idea of other durations. For example, a spell like shield or armor could be maintained indefinitely, perhaps by occupying two first level spell slots. Personally, I am less likely to modify existing spells in this way than to use this approach as a basis for new custom spells. In most cases infinite duration, even at the cost of extra spell slots being occupied, seems like it might cut into the resource management aspect of the game. However, I still think the idea has legs, especially for effects that are more interesting than a simple bonus.