[MaxWilson]

Here's how it actually works: lch is correct that any gems required to cast the spell (fatigue/100) count against the limit without reducing fatigue or increasing paths. You can spend extra gems beyond the required, up to [PathLevel - (fatigue-100)] extra. The first extra gem spent raises your effective level for all purposes, including fatigue reduction (it does NOT cost double fatigue for being under-level). Further gems increase pathlevel ONLY for purposes of fatigue reduction, which means if you're N levels over requirements the spell costs 1/(N+1) times normal. Examples from a test game:

A Helheim Dis has 0 fatigue and 2 gems. She casts Raise Skeletons. She has 1D naturally, and spends 1 gem to boost her level enough to cast the spell. Raise Skeletons is 40 fatigue, and her effective casting level is 2D, and her spellcasting encumbrance is 8. She winds up with 48 fatigue and 1 gem left. The next round she casts Raise Dead, which is also 2D/40 fatigue. She now has no gems left and 96 fatigue.

A Helheim Hangdrott (2A1E3D) has 2 gems and 0 fatigue. He casts Raise Skeleton. Since he is 3D, and since he has 0 fatigue, the combat AI decides to cast it without gems. He is 1 level over, so the spell costs 1/2 normal, or 20 fatigue. Because his spellcasting enc is 8, he winds up with 28 fatigue. He casts Raise Dead the next round, and again does it without gems, winding up with 56 fatigue. The next round he casts again, but his fatigue is starting to creep up so he uses a death gem. Now he is effectively 3 levels over, so it costs 1/3 normal, rounded to 13, plus 8 for encumbrance = 21. He winds up with 77 fatigue and 1 gem left. (Waste of a death gem--it saved him 7 fatigue.) On the fourth round he casts again, using his final gem and winding up at (77 + 21 = 98) fatigue. His buddy the 3A3D Hangadrott, who started with only 1 death gem, also casts and winds up at (77 + 28 = 105) fatigue.

One moral of this story is that gems should not be given to (unscripted) high-pathlevel casters because they'll waste them prodigiously for diminishing benefit.

HTH,
-Max