Magical Conditions of Pandemonium

There are a couple of hitches to casting magic in Pandemonium. One is that, like all the other Outer Planes, Pandemonium has a magical nature that affects spell use. The other's that the plane's physical nature also affects spellcasting.
Sounds confusing? Well, that's the kind of barmy doubletalk spellcasters are supposedly used to dealing with. But it all becomes clearer on a closer look.    

Magical Nature

As an Outer Plane on the Chaos side of the Great Ring, pandemonium imposes the following special conditions by magical school.  

Transmutation

Also encompasses some spells of other schools like fog cloud
Transmutation spells - particularily those that call material into being (like fog cloud), or that reshape matter (such as alter self) - are affected slightly by the chaotic and evil nature of this plane. The chaos bleeds away their energy, shortening their duration by 1 round to a minimum of 1 round. The evil leaches into such spells enough to make them look, smell, sound and feel slightly foul. For example, polymorphed creatures have a sinister touch to their features, create water tastes and smells a bit sulphorous, and so on.  

Conjuration

Creature summoning works as everywhere else in the planes, you can only conjure creatures from the plane you are on. It's worth noting however, that find familiar and wish don't work on this plane.  

Divination

Pandemonium's dark and chaotic nature interferes with spells of this school, making their outcome murky to discern. Whenever one fo these spells is cast, the DM makes a secret Wisdom Saving throw for the caster, to represent a test of will to accurately read the spell's portents. If the saving throw is succesfull, the spell operates normally. Otherwise the DM should give the caster misleading information.  

Necromancy

Also includes Healing Spells and similar Because Pandemonium's on the border of the Lower Planes, there's a slight surplus of background negative energy as compared to positive energy. For that reason, spells that generate life (such as clone and regeneration) are a bit more difficult here. the caster must pass a spellcasting check to make these spell succeed: otherwise they are spent with no effect, the DC of this check equals 10 + level of the spell. On the other hand, necromantic spells that cause damage or manipulate the undead operate without change.  

Wild Magic

Wild magic's enhanced here. This means that spells with a random outcome like chaos bolt or confusion are enhanced here by having the level they are cast on increased by 1. In addition, when a wild magic surge occurs for a wild magic sorcerer or wild magic barbarian, they get to roll twice and choose the result.  

Elemental

Pandemonium's primarily composed of rock and wind, with a bit of water thrown in, but no fire. Consequently, while there are keys to conjure up elementals of earth, air, or water on this plane, there are non for conjuring fire elementals. A mage has got to remember, though, that elementals conjured on this plane are chaotic, with a tinge of madness and evil. That means they're not going to be tractable as normal elementals, which could cause a berk some serious trouble if a command is not worded carefully.

Physical Nature

Some of Pandemonium's special conditions for magic use aren't so much magical in nature as they are a secondary effect of the plane's distinctive features. In a nutshell, it's blasted difficult for spellcasters to cast their spells in the dark, with the wind tearing things out of their hands and howling so loud they can't hear themselves think, let alone speak.   First, the level of noise in most places in Pandemonium is enough to cause deafness, as per the condiction. In more sever locations, it also causes damage like a shatter spell. Similariy, the possibility of miscasting a spell with vocal components becomes a possibility, which is why the DM may request a skill check or percentage roll to cast such spells. Finally, thunder damage can be increased by a die or two as well, for the very loudest of locations.   In addition, spells ihat operate in full or in part by causing sound — things like message, suggestion, the various power words, and so forth — have their effect negated by the wind’s roar. As a rule of thumb, such spells may work fine within 10 feet of their center of effect (DM’s decision). But beyond that radius, there's a chance of negation equal to double that for spell miscast. For example, if the DM decides that the wind is loud enough for a 20% chance of mishap, there's a 40% chance that targets more than 10 feet from the center of effect won't be affected, even if the spell is cast successfully!   But sound isn't the only problem. In most locations, Pandemonium’s wind is strong enough to require a Dexterity check for mages or priests casting spells with material components. If the test is failed, the components are swept out of the spellcaster's hands and carried away in the wind before the spell can be completed. In other words, the spell is wasted: no effect, but the spell slot is still gone.   Similarly, spells that produce cloud effects are useless in Pandemonium’s winds, as are those that produce flames.   To sum things up, then, only a barmy goes to Pandemonium with a repertoire of spells that require lots of material components, that rely on sound to work, or that create effects likely to be blown away. (Here's a hint: Don't take magic mouth or whispering wind.)

Spell Keys

Given Pandemonium’s nature as wind howling through rock, it shouldn’t surprise anybody that spell keys combine those two ingredients, flutes, whistles, and jugs carved from Pandemonium’s stone are commonly used, and they’re held to catch the plane’s wind. Some produce only one strident tone, others multiple, discordant ones. (In the case of the jugs, water from a nearby stream may be added to change the pitch.) Differing tones, combinations, and sequences may act as individual spell keys. Usually, the more grating and discordant, the better. And volume's a consideration: It got to be loud enough to be heard over the howling of the plane itself. Lots of bards come to Pandemonium to experiment with this linking of magic and music (to use the term loosely). A few come away with an insight or two, but even those who don't end up playing with an edge of madness to their music. Tieflings, in particular, make welcoming audiences for such "touched” musicians.

Power Keys

Powers in Pandemonium are reclusive and distrustful compared to those on most other planes. Consequently, they're stingy in their awarding of power keys. When they do give one out, it's most often from chaotic gods (to promote chaos), protective gods (to protect their agents), or ones with a touch for necromancy (to promote evil).