Arcane Magic and the Planes

Planar Pathways: Planewalking wizards and sorcerers have a lot to remember. Certain spells use the Astral or the Ethereal Planes to work. Both planes are accessible from the Prime Material, but this isn't true everywhere. If an Astral-linked spell is cast on a plane where the Astral Plane isn't accessible, the spell fails.
It's easy enough to figure out if these two planes (also called planar pathways) are accessible or not. All of the Outer Planes are connected to the Astral Plane, but none of the Inner Planes are. Similarly, all of the Inner Planes are connected to the Ethereal Plane, but none of the Outer Planes are.

Alterations by School: Arcane spellcasters must also deal with the changes that occur to the various schools of magic on certain planes. Each plane has its own set of physical laws and interactions with the forces of magic. Certain schools of magic can be nulled, enhanced, diminished, or somehow altered. The DM can find complete information for each Outer Plane's magical changes in the DM Guide to the Planes.
In general, though, the following conditions apply.

• Null means that spells of a certain school simply don't work on a given plane. These are usually based on elemental or philosophical opposites. For example, water spells never work on the Plane of Fire. Certain "null" spells may be restored with spell keys, such as Chaos spells on Mechanus.
• Diminished spells function at one level lower than normal. This occurs when a plane's composition and physics aren't conducive to that particular school of magic, but not to the degree that the spells cannot function at all. Spells of 5th level or higher in a diminished school cannot be cast at all.
• Enhanced spells always function as though cast by a character one level higher than the caster's actual level. This happens on planes where that type of spell is conducive to the environment due to similarity or general fostering of such effects; for example, violent evocations on Gehenna mirror the violence of the plane.
• Alterations are by far the most common changes to spells, and their effects vary so much that it is impossible to catalogue them here. Sometimes only the appearance of the spell's effect changes, while other times, the general nature of the spell itself changes.

Spell Keys
Spell keys allow a character to bypass some of the above restrictions. Spell keys enable a character to cast spells so that they function normally on planes where such magic is altered or even completely ineffective, whether the limitation is due to planar pathway restriction or a school alteration. They do this by "attuning" a character's spells to the magical emanations of a given plane.
As extra requirements, virtually all spell keys require a partial action to use. Some spell keys prove far more useful than others to arcane spellcasters:

• General spell keys allow a character to effectively cast any spell from a specific group of spells on a given plane. For example, one general key might restore all Conjuration spells on Baator, while another general key might affect all wall-related spells on Limbo.
• Specific spell keys only affect one particular spell on a specific plane. For example, one specific spell key might restore invisibility cast on Arcadia, whilst another restores power word, kill when cast on Mount Celestia.

Divine Magic and the Planes

Wizards and clerics receive magical power in different ways. A wizard learns them from books, and must contend with the fact that his spells might be altered or nullified, depending on the planar modifications when he casts a spell. A cleric, on the other hand, receives his spells from his deity, and it's simply divine will that the magic isn't affected by planar conditions.

Contacting their gods to receive spells isn't the problem for clerics – wandering into enemy territory is. Here's the chant – the planes – Inner, Outer, and even some of the demiplanes – are territory specifically beholden to one group of powers or another, deities that don't look kindly on interlopers, especially not provocateurs from some other plane. Some deities, especially those down on the Lower Planes, have enough trouble holding to a truce with rivals on their own plane, let aone with gods from planes that differ both morally and physically. All the sodding clerics out to impress their high–ups could make the Outer Planes a very bloody place. Still, putting every priest in the dead–book's only going to make trouble for a deity, and since it's not possible to lock all the doors to a plane, the powers find other ways to suppress the meddling agents of their rivals.

When a cleric character is on a plane other than where his deity resides, his spellcasting power is reduced for every plane between himself and his deity's home plane.
For each plane between the cleric and his deity's home plane, his effective casting level for his spells is reduced by 1. Furthermore, for each separating plane, the cleric loses one prepared spell of the highest level (player's choice).

For example, Nayla the Righteous is a priest leading a band of faithful warriors into the heart of Pandemonium. She is normally a 7th-level cleric. The home plane of Nayla's deity is Bytopia. Moving around the outside of the Great Ring, Elysium, the Beastlands, Arborea, Ysgard, and Limbo all lie between Bytopia and Pandemonium. Therefore, while on Pandemonium Nayla's effective casting level is reduced by 5, and she loses both of her 4th-level spells, and all three of her 3rd-level spells. Nayla casts spells as a 2nd-level cleric (although she has more prepared spells than a true 2nd-level cleric can have).
If Nayla the Righteous leaves Pandemonium and travels to Limbo, there are only four planes separating her from Bytopia. Thus, the penalty to her spellcasting level is reduced to –4, although she doesn't regain any lost spells. If Nayla then moves on to the Abyss, her penalty increases to –6, and she loses one more of her highest-level prepared spells.

Note that Nayla's "power conduit" doesn't trace the shortest route to her home plane, like magical items do. Why? Because the gods don't want it to work that way! It stands to reason that a priest from Bytopia should have a tougher time casting spells on Pandemonium than on Limbo – not everything that powers do is unfathomable, berk. On the other hand, if a priest's deity resides on one of the Inner Planes, he only suffers a –3 penalty to his spellcasting level, as the Astral, Prime, and Ethereal lie between him and his power source. The same limitation applies to those clerics of the Outer Planes who visit the Inner Planes.

Scrolls and magical item are not affected by any of this rival–power/plane stuff, for their powers don't flow from a deity. On the other hand, scrolls are subject to planar conditions, just as arcane spells are.
Furthermore, some magic simply can't overcome the conditions of the plane or location where it's cast – not even with a power key (see above). These conditions are called absolute prohibitions; fortunately, only a few such restrictions exist.

Absolute Prohibitions

Plane	Prohibition
Elemental Fire	No water spells
Elemental Water	No fire spells*
Paraelemental Magma	No water spells
Quasielemental Vacuum	No air spells
Outlands	Gradual nullification of the Spire
Sigil	No interplanar transport spells

* Except in air-filled pockets

Power Keys

A cleric, because a plane's home to his high-up man, can also discover power keys. A power key doesn't key doesn't restore a spell to its normal effect (as a spell key does); it makes a divine spell work even better than before. For instance, a cleric who has the right key can cast Cure Light Wounds and get the maximum effect every time. Power keys are rare, very rare, and the cleric who knows one should count himself a lucky soul. Three kinds of power keys exist, some of them stronger than others:
Specific power keys affect one spell and one spell only. The spell works at maximum power, range, and duration whenever the cleric uses its key in the casting, at the cleric's normal casting level. Specific spell keys are the least likely to be changed by a deity, for they siphon the least amount of the deity's power.
General power keys apply to one entire Domain of spells, improving any spell cast from the group and allowing the cleric to cast spells at his normal level. For example, a cleric with a power key for the Healing Domain could cast everyting from Cure Light Wounds to True Resurrection at maximum potency.
Greater power keys are the mightiest and rarest power keys. They actually reduce the penalties that accumulate as a cleric moves from plane to plane. Depending on the strength of the key, it can bolster a cleric who is separated from his deity by one, two, three, or even four intervening planes. In other words, with the strongest possible greater power key, the reduction to spell casting levels (and the prepared spells lost) caused by travelling the planes is reduced by 4. But those keys are usually reserved for proxies on urgent missions. Most priests should consider themselves lucky to be granted a power key that reduces penalties by even 1.
Power keys are created by the powers themselves, and can change anytime the deity wills it – there's no promise that a cleric can use the same key forever. Odin might teach one of his clerics a rune that's a power key to improve all divinations. If that cleric should foolishly go out and teach this to all his disciples, Odin might get offended and change the power key so that the character's rune no longer works.

The gods use power keys to reward faithful services or as extra muscle on a particularly dangerous quest, and they only pass them out to those who deserve them. A cleric can't request a power key or even find one in a treasure trove. The best guess as to why power keys are so carefully guarded is that each is a direct link to the deity, and costs the deity a tiny portion of its might. Not many powers relish the idea of weakening themselves, so power keys are pretty rare.

Index

The Factions

New Races

Planar Skills

Magical Adjustments

Magical Items

New Spells

Planewalking Equipment