Elemental Stones
by John HareThese stones are found on their respective planes and if used as a focus can increase the potential of spells dealing with its element. These stones are fairly hard to come by and are generally transparent/translucent when found, as spells are cast through them however they slowly turn opaque until they can no longer be used as a focus. Large stones can focus up to 50 levels worth of spells (but these are very rare) Normally stones of about 10 levels worth of spells can be found.
Basically the stone can improve one facet of a spell by 50% (range, area effect, duration, damage) but each spell so improved removes from the stones spell levels the equivalent level. (hmm this doesn't seem worded very well, must be lack of sleep) example Fire Stone with 10 lvls, Magic User casts a fireball through it, increases damage by 50%. After the spell is cast the Fire Stone has only 7 lvls remaining. Note that if there are insufficient levels remaining the spell will not be improved. If the spell is more than double the remaining levels there is a 50% chance that the spell will 1) backfire 2) fizzle 3) produce some unintentional result (perhaps like a wand of wonder :)
Note that these property enhancements only work on the Prime Plane (i.e. Mystara). It is thought that if these stones are used in the creation of a magical item which uses spells related to the element then one facet of the spell may be increased (DM's choice or roll randomly :)
thus wand of powerful fireballs 6d6
* 150% (or 9d6 depending on which you decide when item is created)