Sorcery: Shadow Conjuration/Shadow Evocation

Sorcery: Shadow Conjuration/Shadow Evocation

In D&D, shadow conjuration and shadow evocation were two illusion spells that imitated conjuration or evocation spells in a quasi-real matter. They would be 25% as effective, but if the victim believed them to be real, they would be 100% as effective. How do we do that in sorcery?

First, if we look at the Illusion advantage, we will see that illusions usually require an IQ or Artist (Illusion) roll, and are resisted in a Quick Contest vs. the victim's Perception.

After that, let's look at Partly Limited Abilities on pages 6-7 of GURPS Power-Ups 8: Limitations. Requires IQ vs. Per Roll, -20% can be found on page 17 of the same book. If we apply it only to 3/4 of the ability, that would result in a -20% / 4 * 3 = Quasi-Real, -15% limitation. Done!

And now let's write up the "spell". Fortunately, Patyrsun has some guidelines on his website that I can borrow.

 
    Shadow Magic (Spell)
    Keywords: Varies.
    Full Cost: Varies.
    Casting Roll: Varies. Use IQ or Artist (Illusion) to convince that the illusion is real.
    Range: Varies.
    Duration: Varies.
 
    This is not a spell, but a category of spells that duplicate other spells in a version that is partially illusory and partially real. Thus, Shadow Magic (Fireball) and Shadow Magic (Rain of Stones) are two different spells. The duplicated spell must have an obvious effect that directly affects the subject’s body. Spells without any physical effects, or spells that directly affect mind or body, such as most Mind Control, Communication and Empathy, or Body Control spells, will not work with Shadow Magic. Likewise, Enchantment, Information, and summoning spells will not work with Shadow Magic because they don't produce an obvious physical effect that can be duplicated with an illusion. Additionally, spells that just affect the senses (such as Darkness or Flash) can't be cast in a Shadow Magic version, since they have no visible, physical effect on the subject's body. It is up to the GM to determine which spells have a sufficiently strong physical component to be cast as Shadow Magic.
    If the spell meets the criteria for be cast as Shadow Magic, the mage can cast the spell, taking the same amount of time that he would take to cast the real version of the spell. The subject gets the same roll to resist that he would get against the full version of the spell. In addition, make a Quick Contest of IQ against the subject’s Per. You may substitute Artist (Illusion) for IQ, if it is higher. If the subject resists, he disbelieves the shadowy illusion and is affected at 25% of its power (quarter the damage, quarter the penalties, etc.) If he fails to resist, then he is affected fully. For lasting effects, roll this Quick Contest every minute.
    Statistics: Same as the real spell but with an additional Quasi-Real, -15% limitation that is Requires IQ vs. Per Roll, -20% applied to 3/4 of the spell.