Powers: Control Magic

Powers: Control Magic

GURPS Powers offers the players and the GMs a new interesting advantage - Control. While being versatile and not vague for most of the controllable substances, it is much more difficult to define when dealing with abstract concepts, such as time, space, or magic.

I always wondered how to build an ability that allows the user to transfer, steal, or control existing magical effects. Of course, there is the Neutralize advantage that allows to steal an ability from the user, but it's not quite what I wanted. Perhaps linked Neutralize (with Interruption) and Wild Talent (with Wild Ability) could recreate an existing effect, but it still doesn't feel right, and has daily limitations.

While reading about continous mana in GURPS Thaumatology I got inspired to write this ability based on the Control advantage with Magic defined as a Very Common category. I might've missed something, but here we go:

Control Magic [30/level]
This ability lets you gradually alter the local mana level of a touched subject by taking a Concentrate maneuver and making an IQ roll. When you stop concentrating, you immediately give up control, and the changes revert to normal (unless you take the Persistent enhancement).
- You can decrease the mana level, granting the subject a +1 bonus to resistance rolls against magical abilities and a -1 penalty to spellcasting rolls per level of this advantage. This also decreases the power of magical abilities that do not require any rolls by 10% per level of this advantage (DR becomes 1/10 lower, Allies’ points totals are decreased by 10%, and so on). When used on a magical item, this effect applies to all its magical enchantments.
- You can increase the mana level, granting the subject a -1 penalty to resistance rolls against magical abilities and a +1 bonus to spellcasting rolls per level of this advantage. This also increases the power of magical abilities that do not require any rolls by 10% per level of this advantage (DR becomes 1/10 higher, Allies’ points totals are increased by 10%, and so on).When used on a magical item, this effect applies to all its magical enchantments.
- If you can reach the area of effect of a persistent magical effect, you can attempt to shape or move it. Reach into the effect, take a Concentrate maneuver, and make a Quick Contest of your IQ against the original caster’s spell skill (or other casting attribute, or IQ, if there’s no casting roll). If you succeed, you can reshape the area of effect, as if you were the original caster, and as if the spell or effect in question had the Selective Area enhancement. Additionally, you can move it at a Move equal to your Control level. The target effect needn’t remain in contact with you. Finally, you can increase or decrease the power of the effect by 10% per level of this advantage.
- By touching a target of an ongoing magical effect, taking a Concentrate maneuver, and winning a Quick Contest of your IQ against the original caster’s spell skill (or other casting attribute, or IQ, if there’s no casting roll), you can transfer this effect to another subject you’re touching. Typically, this means transferring a beneficial spell effect from an enemy to you or your ally, or transferring a harmful spell effect from you to an enemy. The new subject does get a resistance roll. If he succeeds, the spell transfer fails, but you may try again. If this advantage has the Ranged enhancement, you can only transfer the effect to a new subject, if the new subject is within 1 yard*level of the original subject. After that, you must keep concentrating to keep the effect from switching back to the original subject. You can do this without keeping the contact with the subjects.
Note: This ability does not allow you to control magical creatures and creations, such as golems, magically animated undead, etc. For that use Mind Control.