The World of Valden
Gestalt characters are highly skilled individuals that undertake campaigns of great importance, reach or lack of allied party members. They are gifted with the ability to gain skills about and beyond even what other adventurers can accomplish.
Each PC starts play with two classes. They must be different classes that would be available at start of play. Even if you could qualify for a prestige class, you could not do so at the start of play. You are still considered a 1st level character. Your classes use the same XP pool, and both level up at the same time. However, you are not considered to be a higher hit dice because of this. Your hit dice will always be equal to your character level. (The level which corresponds to your experience point total)
You can never gain more than one level in any given class per level up. When taking prestige classes, you cannot take the prestige class if you only just qualified in that same level. (For example, you cannot take a level in Arcane Trickster in the same level in which you would gain 2d6 sneak attack or the ability to cast 2nd level arcane spells.)
You cannot, through multiclassing or prestige classes, gain access to spellcasting levels that your character could not otherwise cast. (Example – a character that is cleric 5/wizard 10/Mystic Theurge 10 could not cast 9th level spells as a 15th level character otherwise could not) Caster level and spells per day are not capped. (In the example above the character would have the spell Slot availability of a 20th level wizard but would not be able to prepare any 9th level spells) Open spell slots for levels the character is unable to prepare may still be filled with lower level spells or spells modified by metamagic feats.
Similar to the above, class abilities with the same or similar effects do not stack unless they are specified to do so. (A Rogue/Slayer does not stack sneak attack dice from these two classes, but if he took levels in Assassin they would stack.) In the case where abilities have the same type of function the higher of the two is used. This does not hold true for spellcasting – you simply prepare two different spell lists, even if they are of the same type of magic. (Cleric/Oracle would have two seperate lists, as would a Wizard/Arcanist. In the latter case, however, that character could prepare spells from the same spellbook.)
Each PC chooses two favored classes. Additional favored classes can still be acquired, through racial abilities (Such as the Half-Elf Multitalented) or feats. (Such as the human’s Eclectic or the Half-elf’s Multitalented mastery) You cannot take the same favored class bonus multiple times.
At first level, characters gain the maximum of both hit dice plus their constitution modifier. At every other level, they roll their highest hit dice (minimum half) and gain half the HP of their second highest hit dice. (For example, a Fighter/Rogue would roll a d10, taking half minimum, then add 4 to represent exactly half of a d8.) If you have more than two classes, you do not gain any additional HP. If you have a tie for highest or second highest HP, you can pick which class rolls/adds for HP. (A Fighter/Ranger has two d10, so they would roll a d10 min half and then add 5 to the total. They could choose fighter or ranger for the main roll and ranger for the flat bonus or vice versa.)
Gestalt characters gain the sum total of skill points from both classes they take at level up. They gain all class skills listed from every class they have levels in. There is no effect for having multiple classes with the same class skills.
Characters take the best version of their save progression from base classes. Prestige classes are added as normal.
Because having multiple classes leads to needing to support different sets of abilities, gestalt characters gain an additional feat at 1st level, and gain an additional feat at levels 4th, 8th, 12th and 16th.
Class based character restrictions still apply (Such as Paladin Code of Conduct and Druid Class Restrictions) but depending on the situation might be allowed some flexibility given purpose of the class. (For example: A Paladin/Inquisitor wouldn’t be able to get away with as much as an Inquisitor, but would be able to get away with more than a Paladin)
Feats that generally apply to an ability shared by multiple classes can be used with any instance of that class. Feats that add usages to certain abilities when you have two classes with the same or similar ability do not apply twice. (Example: A Cleric/Oracle with two channel energy abilities can use Selective Channeling for both instances of channel energy, but only gains two additional usages of Channel per day, and you can choose which set of pools each additional channel uses.
Rules are subject to change, but player will be allowed to make build changes based on the severity of rule changes.