Rednog's Layering Spell
(Alteration, Enchantment/Charm, Metamagic)

Range:  0
Components:  V, S, M
Duration:  Special
Casting Time:  3 hours
Area of Effect:  Creature touched
Saving Throw:  Negates

This spell allows the caster to apply a "layering" effect to spells which are normally not cumulative with each other. It does not matter if these spells are wizard or priest spells. All spells which are to be layered have to be cast in immediate succession beginning the next round after finishing this spell. Once this casting has stopped, no additional spells may be added to the layering effect. Thus, it would be possible to layer several stoneskins over each other; to create a multiple haste effect, etc. This spell allows a maximum stacking effect of one additional spell per 3 caster levels to be in effect on one creature (it would be possible for a 21st-level caster to allow a stacking effect of three additional hastes, one stoneskin, protection from fire, protection from lightning, and a prayer spell on one creature in addition to already existing versions of these spells on the same creature). It is not possible to cast this spell on a creature which already has this spell in effect. Thus, this is the only spell which may not be layered or stacked with itself. The duration of this spell is the duration for a single additional 1st-level spell. It is reduced for every additional level of each additional spell by one day; once one day or less is left, it is reduced by one hour in the same ratio, until one hour or less is left. Now decrease by turns until one turn is left, then decrease by rounds to a minimum of one round. Thus, our 21st-level wizard, who would stack seven 9th-level spells (one spell of 8 levels higher than first level plus 6 spells of 9 levels higher than a 1st-level spell would make 62 units) on himself would have a duration of 101/2 days for a single 1st-level spell; it would first be reduced by 10 days (leaving 52 units and 1/2 day, or 12 hours duration), then by 11 hours (leaving 41 units and 1 hour duration left over), then by 5 turns (leaving 36 units and 10 rounds), then by 9 rounds to 1 round minimum (actually leaving 27 units) and only a single round of duration. Thus, it is not very good to layer too many high level spells as they run out almost immediately. Once the duration of this spell runs out (or it is dispelled), all layered spells end immediately. This spell may also be applied to spell-like effects.
Note: the layering effect is only additive: thus, 6 hastes don't give 2?2?2?2?2?2 = 64 times all attacks but only give a multiplication factor of 12.
This spell has a significant negative side effect: as layering causes such a concentration of magic, it causes all boundaries of magical items to be significantly weakened. It is therefore possible that magic items and permanent spells are permanently destroyed in a most violent fashion. In case of a permanent spell, the chance that this happens is a base 100% minus 10% per spell level of the permanent spell. In case of an item, the chance is 100% minus 10% per spell level of the highest powered effect of the item, similar to any existing spell or minus 15% per plus, in case of an item with plusses (whichever is the higher of the two modifiers). Next, add 1% per spell level layered on the creature.
If a spell or an item is destroyed by this spell, the magic contained will not pass away quietly. It causes an explosion of spellfire doing 1d10 hit points of damage per contained charge or per spell level which was destroyed in a 1-foot per charge or spell level destroyed radius sphere. As this is spellfire, only a wall of force will prevent others from taking damage (no other resistance helps: not even magic resistance or immunity to fire); the target creature takes full damage no matter what resistance it normally has (as it cannot encase itself with a wall of force).
The material component is a block of mithril which is made up from two layers of mithril for each spell level to be layered and a single scroll for each spell which is to be layered. Each scroll has to be completely encased in a thin coat of mithril. This block then has to be speared with an adamantine spike which was broken on an anvil and then fixed again with one mending spell per spell level to be contained in the block. The whole mithril block without the scrolls costs no less than 3000 gp per spell level it is to contain (thus, our 21st-level wizard above would have wasted 7 scrolls containing a single 9th-level spell each and a full 7?9?3000 gp = 189,000 gp).

