Most classes function exactly as described in the Pathfinder Core Rules, the Advanced Player’s Guide and/or Ultimate Combat. The exception is any of the spellcasting classes. As this is a low-magic campaign, I have decided to limit the use of magic in the following manner:
Casting a Spell
When an arcane caster attempts to cast a spell, they must first succeed at a Spellcraft check, the DC of which is equal to 15 + the spell level. The caster may take 10 or take 20 on the check, but doing so takes 10 or 20 times as long to cast (as appropriate). If the check fails by 5 or less, there is no effect and the spell slot is not expended. If the check fails by more than 5, there is no effect and the slot is expended. If the check is a natural 1, the spell misfires and will somehow go wrong. The exact details vary with the spell, but will always be detrimental to the caster and his allies.
For divine spells, the caster must succeed at a Knowledge (religion) check, the DC of which is equal to 15 + the spell level. As with arcane casters, the character may take 10 or take 20 on the check, at the cost of an extended casting time. If the check fails by 5 or less, there is no effect and the spell slot is not expended. If the check fails by more than 5, there is no effect and the slot is expended. If the check is a natural 1, there is no effect and the caster has offended their deity and must spend at least an hour in devout prayer before any of their spells will work.
The Price of Power
In addition, magic is very taxing to use. All but the simplest of spells draw upon the caster’s personal power reserves or is otherwise physically taxing (as channeling the power of a deity tends to be). To this end, each time a spell above 0-level is cast, the caster must make an Constitution check of a DC equal to 10 + the spell level. If the check fails, the caster is fatigued until he or she rests for a number of rounds equal to the level of the spell that caused the fatigue. If the caster is already fatigued for any reason, he or she becomes exhausted, instead. The +4 bonus for the Endurance feat can be applied to this check.
It should go without saying, but these restrictions apply equally to PCs and NPCs.
On Magical Items
Given the requirements for casting spells on Jenneria, it should come as no surprise that there are no “magical sweatshops” where wizards slave away making +1 swords. With the exception of fairly simple potions and the occasional scroll, magic tends to be both rare and wondrous. A typical magical item was crafted for a specific person or purpose. Almost never are any two exactly alike. Even two mere +1 daggers would be very different in design, representing the skill and origins of the one who crafted them, and the purpose or individual for which they were crafted.
A successful Knowledge (History) or Knowledge (Local) check will often reveal something about the origins of a magical artifact; the DC being dependent on the item in question.
Magical items beyond potions or scrolls (and perhaps the occasional wand) are almost never found for sale. Those who have them tend to covet them, and the price of even a simple +1 club is a fortune for most people. Even most merchants are unable to match an item’s true value, and they realize that even if they could afford to purchase it, it is likely that no one could afford to buy it from them in turn.
RANGERS & PALADINS
In a low-magic campaign, rangers and paladins lose their hybrid ability to cast spells, but gain several other abilities to replace them. Archetypes remain unchanged except for those that lose spellcasting ability, which lose these special abilities listed below, instead.
paladin, with the following changes and additions:
Spells: The paladin does not gain the ability to cast divine spells.
Blessed Weapon (Su): Any melee weapon wielded by a paladin of 6th level or higher is treated as good-aligned for the purpose of overcoming damage reduction.
Divine Might (Su}: At 11th level and higher, the paladin can use a standard action to add a +4 bonus to her Strength, Wisdom, or Charisma score. This ability may be used once per day, and its effect lasts for 1 minute per class level.
Tend to Mount (Su): A paladin of 13th level or higher who uses her lay on hands ability to heal her mount cures 5 points of damage per point of healing spent. In addition, the paladin may use her lay on hands ability to end any one of the following adverse conditions affecting her mount, at the cost of 5 points of healing per condition unless otherwise noted: ability damage (costs 1 point per ability point restored), blinded, confused, dazed, dazzled, deafened, diseased, exhausted, fatigued, feebleminded, insanity, nauseated, sickened, stunned, or poisoned. The paladin can remove adverse conditions at the same time that she heals damage, but any points of healing spent to end adverse conditions don’t also cure hit point damage.
Holy Sword (Sp}: Ar 16th level, a paladin gains the ability to use holy sword once per day, as a caster whose level is equal to one-half the paladin’s class level.
Spells: The ranger does not gain the ability to cast divine spells.
Fast Movement (Ex): At 6th level, the ranger’s base land speed increases by 10 feet. This benefit applies only when he is wearing no armor, light armor, or medium armor and not carrying a heavy load.
Nature’s Blessing (Su}: At 11th level and higher, the ranger can use a standard action to add a +4 bonus to his Constitution, Dexterity, or Wisdom score. This ability may be used once per day, and its effect lasts for 1 minute per class level.
Healing Touch (Sp): Once per day, a ranger of 13th level or higher can use either neutralize poison or remove disease, as a caster whose level is equal to one-half the ranger’s class
Freedom of Movement (Sp}: A ranger of 16th level or higher can use freedom of movement on himself once per day, as a caster whose level is equal to one-half the ranger’s class level.