Paths of Westholm
Magic, which flowed freely and evenly throughout Westholm prior to the Cataclysm was forever altered by that event.
The Arcane energies that power all magics in Westholm now flow in turbulent and ever-shifting currents. Each region has its own magical “climate,” but even within these broad climates the Arcane Currents are subject to frequent shifts. Very large magical events may even shift the basic climate of a region and/or its neighbors.
The way this is realized in the gaming mechanics is with skill rolls associated with casting. You can roll against Knowledge (Arcane Currents)—a custom skill for this campaign—to try to cast the spell as normal in any given magical “climate.” The DC check for this skill will vary depending on how extreme the “climate” is. If you do not have Knowledge (Arcane Currents) or fail the skill check, then you face the below effects:
In Low Magic Areas:
1) You must roll against your Will defense
2) If you fail, you fail to cast the spell. If you succeed the spells effects are reduced by a die (so 1d6 damage becomes 1d4 damage, if it lasts for 1d10 rounds then it lasts for 1d8 rounds)
3) A critical success negates the die reduction. A critical failure “saps” your energy and keeps you from casting anything for 1 round.
In High Magic Areas:
1) You must roll against your Fortitude defense
2) If you fail, you take 1d4 damage instantly and fail to cast the spell. If you succeed you may make a reflex save to avoid the 1d4 damage and the spell’s effects are increased by a die (so 1d6 damage becomes 1d8 damage, if it lasts for 1d10 rounds then it lasts for 1d12 rounds)
3) A critical success “invigorates” you, turning the 1d4 damage into 1d4 temporary hit points. A critical failure deals 1d6 damage and forces you to make a reflex save or suffer the spells effects yourself.