Alignment is a cornerstone of the Pathfinder Roleplaying Game. In its most useful form, alignment is a shorthand to help players learn more about their characters' personalities. But sometimes you may want to play in a world where there is no absolute good and evil. Perhaps the only lord willing to send troops to aid the PCs' fight against an undead horde is an oppressive dictator who will use the situation to further his own power and oppress his subjects—but without his help, everyone will die. Or the PCs must face an infernal foe, but the only available way to take him down is to imbue themselves with demonic power.
In the following rules variant, the PCs can test their convictions against impossible situations and make decisions without players feeling constrained by the mechanical consequences their characters will suffer if their alignments change. Alignment is replaced by a new character aspect called loyalties, and class alignment restrictions are redefined in those terms. Several options for handling alignment-dependent spells and effects are presented here.
When you use the loyalties system to build a character, whether a PC or an NPC, decide on three loyalties. These can represent ideals, people, organizations, or anything else to which the character is loyal, and might be as abstract as "my honor" or as concrete as "my beloved mother." Rank these loyalties from strongest to weakest. One easy way to decide the order is to ask yourself what your character would do if these loyalties came into conflict. For a more simplified game, you could use one or two loyalties. These loyalties then replace alignment as the standard by which characters' actions are measured.
During play, a character might take an action that causes him to change loyalties, just as a character in a game with alignment might have to change alignment. Whether this has any mechanical impact depends on how the GM has chosen to deal with loyalty-based restrictions and effects.
Certain classes depend on alignment features. Below is a list of changes you'll need to make to the classes from the Pathfinder RPG Core Rulebook if you decide not to use alignment—you can use these as a guideline to change other classes as well. These assume that you've replaced the default alignment system with the aligned loyalties option outlined below under Creatures, Spells, and Effects—if you have gone further and removed even these basic alignment elements (as in the subjective morality option), then ignore all references to loyalty restrictions in the classes below.
Barbarian: Remove the alignment restriction. A barbarian may not have a loyalty to law, order, or any similar concepts.
Cleric: Remove the alignment restriction. Clerics must have a loyalty to their deity, though not necessarily to a church hierarchy or other clergy. Remove the restriction against casting spells of certain alignments (since such spells no longer exist), but create a list of spells that each deity would ban based on his or her portfolio and personality. Remove the Chaos, Good, Evil, and Law domains from all deities' lists, and replace them with appropriate domains so each deity has the same number of domains.
Druid: Remove the alignment restriction. Druids must have a loyalty involving nature or the druidic code of conduct.
Monk: Remove the alignment restriction. A monk who ever has a loyalty to chaos, imbalance, or closely related concepts becomes an ex-monk for as long as he has those loyalties.
Paladin: Remove the class's alignment restriction. The paladin's code of conduct becomes "A paladin's code requires that she respect legitimate authority, act with honor (not lying, not cheating, not using poison, and so forth), help those in need (provided they do not use the help in a way that betrays any of the paladin's loyalties), and punish those who harm or threaten innocents." Remove the Associates section under the code of conduct. A paladin must have a loyalty to the concept of good, and most paladins also have loyalty to a deity. For changes to the paladin's detect evil ability, see the Creatures, Spells, and Effects section, below. Creatures whose loyalties are in opposition to the paladin's gain no benefit from the paladin's aura of justice ability.
The paladin's smite evil ability works against any foe whose loyalties are directly contrary to the paladin's highest loyalty. She can also recover one use of smite if she accidentally smites an invalid target. She can do this a number of times per day equal to her maximum uses per day of smite. This means the paladin isn't punished for having to guess, but she also can't use her smite class feature on every opponent as a de facto loyalty detector. If the paladin's highest loyalty is to good, she can smite foes with a loyalty to evil, but if her highest loyalty is to her king, her smite might instead apply to foes with loyalties to the jealous baron's rebellion. The GM has the final say on how the ability works, since only the GM knows the NPCs' true loyalties—a mercenary who works for a cause might not have a loyalty to that cause, for example. The GM can decide to simply have smite work only on foes with a loyalty to evil, or to require the paladin's highest loyalty be to the concept of good.
Full Removal: You can remove alignment-based spells and effects entirely. Consider replacing monster spell-like abilities with others of similar power. You'll need to replace other abilities that affect creatures of particular alignments (such as the heavenly fire ability of a sorcerer with the celestial bloodline) or restrict character options to avoid such abilities.
Aligned Loyalties: You can allow alignment-based effects to instead apply to characters who have loyalties to the concepts of chaos, evil, good, or law (or any concept close enough).
Outsiders Only: You can keep the alignment subtypes for outsiders and allow alignment-based effects to apply only to them. In this style of game, mortals live in a world with shades of gray, but true evil does still exist in the multiverse in the hearts of daemons, demons, devils, and the other evil outsiders.
Radiant and Shadow: You can instead have alignment-based effects apply to everyone, or nearly everyone. Remove the alignments and replace "good" and "evil" with stand-ins that lack moral implications, such as "radiant" and "shadow." These are then treated as simply two more forms of energy that exist in the world, and any creature can wield a weapon that deals radiant or shadow damage. You'll need to make appropriate changes, such as changing DR 5/good to DR 5/radiant, making unholy weapons, shadow weapons, and so on. Creatures that were once strongly defined by their alignment become more unpredictable. Maybe some angels are just as corrupt as devils, despite their celestial forms, and the PCs must team up with a noble demon and wield shadow weapons to defeat their foe. You can choose to grant certain creatures immunity; for instance, perhaps angels don't take radiant damage from radiant weapons or radiant smite, the stand-ins for holy weapons and holy smite.
Subjective Morality: You can make your world extremely complex by replacing all alignment-based effects with subjective morality based on loyalties. In this kind of game, everyone is the hero of his own story, and the only alignment-based items and spells that exist are the ones named after the good alignment (such as holy weapons and holy word) plus detect evil. However, these effects apply not to good in the usual sense, but instead depend on the loyalties of their users. When someone uses detect evil, it detects others who have loyalties that oppose the caster's. When a character wields a holy weapon, it deals extra damage to those with conflicting loyalties, and so on. It's up to the GM to decide when loyalties conflict. For instance, if a magus decides that his primary loyalty is to himself, he could not reasonably claim that everything that ever attacks him has a conflicting loyalty, but an enemy who constantly abused him in the past would have a conflicting loyalty. Against this enemy, the magus's holy attacks would strike true. This world might even do away with the idea of loyalties to the concept of good and allow paladins and antipaladins alike to use the paladin class and smite each other. Since even outsiders no longer have an alignment subtype, you'll need to add other subtypes to the list of choices for abilities such as bane or a ranger's favored enemy class feature. This covers subtypes such as demon or devil, but some outsiders have no non-alignment subtype. If you want such creatures to be subject to these abilities, you could lump them together under a new subtype (such as "independent"), or add subtypes on a case-by-case basis—the astral leviathan might have the "astral" subtype, for example.