Those with ritual path magic have an infinitely flexible magic system at their fingertips. So how to make a one-spell johnny? Or those who have an innate ability to do one particular thing. To create such abilities use the following method:
• Determine the ritual normally using the standard rules for ritual path magic.
• Purchase Magery 0 (Limited Scope, One Spell only, -80%) [1], Discreet Ritual (Pyramid #3/66: The Laws of Magic, p. 11), the Path skill at IQ+0, and Ritual Mastery. Buy enough levels of Ritual Mastery (which, for this one purpose has unlimited levels with each +1 translating to another level) to cast it so that your effective skill equals or exceeds the Safe Threshold (GURPS Thaumatology: Ritual Path Magic, p. 26) to cast the spell plus 4. . Treat the Path skill as if it were IQ/Average for this purpose instead of IQ/Very Hard (you’re effectively double specializing in a Path, see Pyramid #3/66: The Laws of Magic, p. 20).
• Ignore the usual restriction on Thaumatology. Those with knacks just do things with the smallest act of will! This comes at a price however – they cannot create conditional spells with their ability and can only alter normally alterable effects (e.g., Range or Subject Weight). Optionally, they can create a single form of conditional ability (e.g., an elixir), but cannot cast it normally.
• Optionally, purchase Magery (Limited Scope, One Spell only, -80%) [2/level], Ritual Mastery [1], or Ritual Adept (Limited Scope, One Spell only, -80%) [8].
• Those without adept still suffer the rules for connection, consecrated space, etc.
• Determine casting time as follows: if the character is a non-adept then it takes a minute to cast. If he’s an adept it takes a single second to cast. If you’re an adept you can opt perform an action instantly by buying Compartmentalized Mind 1 (Limited, One Spell only, -30%) [35].” You may do this once per turn as a free action.
• Add up the final cost and treat the whole thing as advantage.
Example
Mercado can cast a spell with the ability to drown a nearby target. The player decides that the Nixie’s Curse spell (GURPS Thaumatology: Ritual Path Magic,p. 47) is what her character wants as a knack. Theia’s player then buys Magery 0 (Limited Scope, Nixie’s Curse only, -80%) [1], Discreet Ritual (Nixie’s Curse) [1], Path of Matter (Create Water) (A) IQ+0 [2], Ritual Mastery (Nixie’s Curse) [1], and Ritual Adept (Limited Scope, Nixie’s Curse only, -80%) [8]. Since Nixie’s Curse takes 90 energy to cast he must have a minimum skill of 23 (to cast the spell) + 4. Since she has a IQ of 14 that means she needs to buy nine more levels of Ritual Mastery so that it equals IQ+11. This is written down on Theia’s character sheet as “Ritual Path Magic Knack (Nixie’s Curse) [22]” and allows Theia to cast Nixie’s Curse at IQ+13 in one second with merely an act of will. If she wanted to drown someone as a free action it would cost another 35 points.