OK, new problem. My players were looking at the options for increasing casting time in OLD and ran into some confusion: The table suggests that increasing time actually reduces MP cost but the paragraph description for what increasing casting time does indicates that MP costs shouldn't be reduced. Here's a quote from my player's email:
I have read a few spells in the grimoire; and it looks like they are actually subtracting MP from the costs of spells using longer casting times; as the table suggests. Example:
Mind Wipe Compel Person Cost 14 MP; Skills compulsion 6 Casting Time 1 minute Duration 1 day Range touch; Target one humanoid creature You spend a minute modifying the target’s mind, erasing the subject’s memories and knowledge, leaving him with the mind of an infant. The subject is unaware that his mind has been altered. The subject’s memories return at the end of the spell’s duration. Costs 6 MP mindwipe, 3 MP subtle compulsion, 6 MP duration, 1 MP range, –2 MP casting time.
This contradicts the paragraph on p166:
Both quantum realities can't exist at once! Which is correct?Casting Time (Reduction). Spells normally take 2 actions to cast. By increasing the casting time, you can exceed your normal maximum MP limit—you can reduce the effective MP cost of the spell for the purposes of determining the maximum MP you can use on one spell, but you still need to actually spend the original MP cost. You cannot reduce a spell’s effective MP by more than 50% by increasing the casting time; neither can you reduce it to 0 MP. If interrupted during casting, the spell fails, the time spent is wasted, and the full MP is still expended. To cast a spell faster than 2 actions, you need to take certain exploits, such as Signature Spell.