This is a simple house rule designed to address my issues with evocation in the DFRPG mentioned last week. The specifics are largely derived from the aquarium scene in Small Favor (and may include very minor spoilers).

Reserving Power

A character with Evocation may choose to draw power without immediately using it. Drawing power is an automatic, supplemental action performed once per exchange (often immediately before casting). The character can draw shifts of power up to Conviction for 1 mental stress. Each shift of power drawn beyond Conviction increases this stress by +1 (Conviction 3 drawing 5 power would take a 3 stress hit).

This power can be used immediately or reserved. A caster can continue to draw power on subsequent exchanges, even if already reserving power. Multiple exchanges of reserved power are treated as a single pool (i.e., they are not tracked individually per exchange). Any unused reserved power is lost (harmlessly) at the end of the scene.

If the power is used immediately, the evocation roll proceeds normally.

If some of the power is reserved, the amount used for any particular evocation roll is treated as the difficulty of the roll for fallout/backlash purposes (e.g., if a wizard draws 5 power but only uses 3, saving 2, the difficulty for the Discipline roll is 3, and all elements of the spell will proceed as if the wizard had only used 3 power; the wizard will then have 2 left over for another spell on the next exchange).

Reserving power stores magical energy inside the caster’s body in a way that is uncomfortable at best, and requires concentration to maintain.

A character that has at least 1 shift of power reserved by the end of his or her turn gains the temporary aspect “Reserving Power.” This aspect can be assessed as a supplemental action by any other caster by succeeding at a roll of Lore vs. the target’s Discipline (the GM may provide a bonus to this roll if the caster is reserving a lot of power, at his or her discretion). The aspect can be tagged for any roll that would benefit from the caster having split concentration, or for an attack on the reserved power (see below).

Another character that believes the caster is reserving power (either through the assessment or just guessing), can attempt an attack to upset his or her concentration. The skill used for the attack is anything that would make sense distracting the caster enough to lose focus, and it is resisted by the caster’s Discipline (i.e., it’s similar to a maneuver, but it does damage). If the attack succeeds, the shifts convert reserved power instantly to Backlash on a one-for-one basis (up to the number of shifts of power reserved). For example, a wizard reserving 3 shifts of power is distracted with 2 shifts, immediately taking a 2 shift backlash hit and leaving only 1 shift of power remaining. If the distraction had gotten 4 shifts, the wizard would have taken a maximum of a 3 stress backlash hit (and had no power remaining).

Ambient Magic

Most casting uses the natural background magic of the world: the caster draws it in, shapes it, then sends it back out as a spell. Stress from evocation represents the exhaustion this exercise causes.

Some places may have higher than normal background magic (represented by an appropriate aspect) where drawing in power is less tiring because it is easier to gather. A caster may tag this aspect to treat Conviction as +2 when drawing power in that area. For example, in Storm Front, after Harry had assessed the “Power in the Storm” aspect on the story, he could tag that aspect to draw up to 7 power (Conviction 5 +2) for only 1 mental stress whenever he had access to the storm’s energy.

Other places may have reduced background magic (also represented by an appropriate aspect). This aspect may be compelled during a power draw to reduce the power gained by half (round down); stress is still dealt at the amount intended for the draw. For example, Harry is trying to stop a massive ritual for which the villain has been channeling massive amounts of power for quite some time. He attempts to draw 6 shifts of power and the GM compels the “Massive Ritual” aspect; if Harry’s player accepts, he’ll only gain 3 shifts of power and still take 2 mental stress (but will get a shiny fate point).

Rare places (like being trapped in another wizard’s circle) may cut the caster off from background magic entirely. In these cases, the caster is limited to power currently reserved before being trapped, or his or her own life energy. When drawing on personal life energy the entire power draw is treated as a single physical attack (which can be reduced with consequences normally), and the normal stress cost (1 + excess beyond Conviction) is treated as a second, mental attack. For example, if Harry (Conviction 5) tried to draw 7 points of power when in a magical dead zone, he would take 7 physical stress and 3 mental stress. GMs are encouraged to reward casters very heavily with Fate points for trapping them in a magical dead zone.