I'm curious as to why only three collers keyed to any given ring. Seems pricy at that level.Now, if you could key any number of collars to the ring, that would be different.
Hmm... perhaps price the Shocking Grasp on the collar, rather than the ring....
3/day, 1st level spell, caster level 2, "command word".... spell * caster * 1800 /(5/3) = 1*2*1800*(3/5)=2,160, and let the control ring locate the collars (locate object, rather than creature; it finds the collars....) 2nd spell level, caster level 3, "command word", at will: spell * caster * 1800 = 2*3*1800=10,800.
Also, the "locate" line is limited to Long range (400 feet + 40/ft level) so the controller pretty much has to be in sight of the slave....
Edit: Let's see.... with the Locate Object / Shocking Grasp pairing, you can manage 20 collars on one master ring for about the same price as the original setup for three collars. which would probably be attractive enough for any long-term slave-trader.
Hmm.... if you make the shock aspect at-will, and put it on the control ring....
Collar: 500 gp
Control Ring: Locate Object: 2*3*1800=10800 base for the locate Object, 1*3*1800=5400 base for the shock (at 3d6.... but the potential for controlling how hard to zap, for 1d6, 2d6, or 3d6....) for a control ring priced at 10800+1.5*5400=18,900; capable of shocking anyone wearing an attuned collar as a standard action.
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