[Magic] Loophole in the “Tickle” spell

[WingedKagouti]

Originally Posted by VIVIT

One the sillier spells in GURPS Magic is Tickle—a Magery-0 Body Control spell with a prerequisite count of 2 that lets you afflict the subject with a seizure (!?) for its duration of one minute. This is surprisingly potent for such a low-level spell, but it's balanced by the fact that it requires continual concentration—the idea presumably being that the caster must actively exert some sort of telekinesis-like force to do the tickling.

There's one problem, though: spells that require active concentration don't terminate when you stop concentrating. You can resume them at any time. This seems to mean that with a single casting of this spell, you can inflict several seizures by concentrating intermittently. Since a seizure inflicts 1d fatigue when it ends, you could, in theory, use this spell to very quickly drain someone of all FP.

Note that spells which require concentration do not change state while you're not concentrating (even if they don't end until you fail to maintain them). You'd have to spend a turn concentrating to pause the effect and then another to resume. This will give the target 1 turn to do something every other turn, while also requiring that the mage use all their time messing with that target (and moving the single step Concentrate allows).

And a GM is certainly within their rights to say that a 1 second seizure is not enough to cause someone to lose much/any fatigue, though in the spirit of fair play they should use the same ruling for NPCs and PCs. If you think it's an issue in games you run, you could always rule that it's 1d6 fatigue capped by the amount of turns in seizure.

Also, if you want to cast any additional spells you take a -3 per spell you're concentrating on instead of the usual -1 per maintained spell.

Lastly, it costs 5 energy to cast (and maintain), so even with skill 15+ you're looking at 2-3 casts for the vast majority of mages without tapping into a Power Stone or resting. As it's a Regular spell it takes a -1 to skill for each yard between the target and the caster('s staff) and it increases in cost for larger targets.