Spells & Magic House Rules

The following house rules apply within the environs of the Eastmark. Deep within the Realm of Man magic is further restricted, becoming less and less reliable as one ventures into the domain of Law.  It is said that the faerie races become increasingly uneasy as they pass Herdley towards Royal Dunfalcon.  North and east beyond the Eastmark lies the Realm of Chaos, where magic is said to be more powerful still.
It is said that the competing Realms of Law and Chaos are not fixed, but fluctuate according to the fortunes of Man. The establishment of Wizards' Towers and similar edifices will commonly enable the employment of higher-level magics.

(1) Maximum Spell Level
LOW:
Magics of up to the 2nd rank may be employed in Tilea and in Neria, deep in the Realm of Law, but most require active concentration. Gunpowder functions normally.
LOW-MEDIUM:
Magics of up to the 3rd rank may be employed in Dunfalcon, and around Lake Neme.  Gunpowder functions normally only in large quantities. Fireball has a 10' diameter. Charm is ineffective in combat and periodic saving throw always applies. Once saved, cannot be recharmed.
MEDIUM:
Magics of up to the 4th rank may be employed in Herdley (from Herdley Ridge north), Kallent, and Redfort. Gunpowder is increasingly unreliable as one travels north. Fireball has a 20' diameter. Charm periodic saving throw always applies. Once saved, cannot be recharmed.
MEDIUM-HIGH:
Magics of up to the 5th rank may be employed in Yggsburgh and most of the Eastmark, Talworth & Easmoor, and lands to the west of the Eastmark. Gunpowder is non-functional here, except in the hands of certain weapon-bonded individuals. Fireball has a 30' diameter. Charm can be recast to prevent periodic saves, but  once saved, cannot be recharmed.
HIGH:
Magics of up to the 6th rank may be employed in Gaxhill & the Little Hillwood, in lands far north of Yggsburgh, in Dradvil around the Purple Tower, and in Easterling-ruled lands east of Talworth. Fireball has a 40' diameter.
VERY HIGH:
Magics of up to the 7th rank may be employed in the Wychwood. 
Magics of up to the 9th rank may be employed within Castle Zagyg.
It is possible that magics beyond the 9th rank may be employable in places of great sorcerous energy during specific planar conjunctions - when the 'Stars are right'.

(2)Concentration
Within the Eastmark (excluding Castle Zagyg) the following spells require caster concentration, and end if the caster casts another spell or falls unconscious.

Level 2
Invisibility (self only, no gear/clothing)
Levitate (must maintain line of sight to creature levitated)

Level 3
Fly (self; requires broomstick, carpet or similar spell focus)

Powerful Wizards who wish to employ spells while flying typically seek out flying steeds (hippogriffs, griffins, or even dragons), or seek to craft devices such as permanent flying carpets, which can remain hovering while the wizard wreaks havoc on unfortunates below. It is speculated that the Archmage Zagyg employed such to break the Siege of Yggsburgh in YY 1.

(3) Polymorph Other:  Within the Eastmark (excluding Castle Zagyg) this spell may only transform the recipient into a basically inoffensive natural creature (eg frog, goat, pig, rat) of size no larger than the recipient.  The environs must not be inherently lethal to creatures of that type (polymorph to fish only works in water).  Undead are transformed into undead versions of these natural creatures, demons into demonic versions, etc.