The 3.P Tiered Gestalt Rules were intended to solve the single most important issue with the D&D 3.5 / Pathfinder system, but a few more house rules are necessary (mostly for high-fantasy / high-power play). See also the 3.P Gameplay House Rules once you've completed character creation.
In no particular order:
These aren't new rules, but they bear repeating.
Ledge Campaigns use the Pathfinder rules by default, with D&D 3.5 content converted to these rules. Players wanting to use D&D 3.5 content can review the Pathfinder Roleplaying Game Conversion Guide for specifics, but a few general rules / clarifications are provided below:
In principle, Ledge Campaigns allow classes and options from all books and all sources. This includes third-party published books, magazines, and other supplemental products. In practice, first-party sources and select third-party sources are preferred. Additionally, some sources don't clearly fall into either category. To distinguish between true-first-party sources, quasi-first-party sources, preferred third-party sources, and other third-party sources, we use the following definitions:
FIrst-Party Sources: Anything designed and published by Wizards of the Coast for D&D 3.5 or Paizo for Pathfinder. Examples here would be the Player's Handbook / Core Rulebook, the Dungeon Master's / GameMastery Guide, or the Monster Manual / Bestiary for each edition.
Second-Party Sources: Anything published, but not necessarily designed, by Wizards of the Coast or Paizo (such as the Dragonlance books). Anything designed by Paizo for D&D 3.5 (such as the Dungeon and Dragon magazines). Anything designed by a third-party publisher or fan community with the blessing of Wizards of the Coast or Paizo (such as the Dark Sun books). Any preferred third-party publishers (such as Dreamscarred Press, Drop Dead Studios, or Lost Spheres Publishing).
Third-Party Sources: Anything not published by Wizards of the Coast or Paizo but designed for D&D 3.5 or Pathfinder and not expressly listed as a second-party source.
See 3.P First, Second, and Third Party Sources for a listing of all sources by category.
For especially high-power / high-level campaigns, players can expect to become mythic characters. The Epic rules and options from D&D 3.5 are banned, but we plan to replace many of them with homebrew material or house rules as time goes on. In the meantime, players can reference the 3.P Mythic House Rules for details.
Exactly when player characters become mythic will vary between campaigns and groups, and is meant as something of a surprise. For planning purposes, you can assume that you'll be able to complete your mythic progression before reaching 20th level. This may mean that you gain mythic tiers each level from 11 to 20, or by some slower progression starting from an earlier level. As with leveling, players within the same group will progress at the same rate, barring a few exceptions (such as a player declining mythic status or suddenly gaining an avataric power).
Mythic tiers and their associated abilities do not cost CP, and Mythic Paths cannot be gestalted.
We'll use the Ability Point Buy system for starting ability scores (High Fantasy / 20 points).
Players may level up their characters in any order.
For example, you could choose your feats before you select your classes for that level. This may mean that characters can qualify for some prestige classes or other options earlier than normal. Just make sure to take notes so you can explain your leveling process to the GM.
We'll be playing with the Automatic Bonus Progression rules with a few changes.
First, any player aligned with at least one of the main factions in a Ledge Campaign can expect to receive their full wealth by level (rather than half per ABP). This is the primary benefit of working with these factions, and we encourage players to consider their aligned factions during character creation. You may begin with full wealth if you're already aligned with a faction.
Second, the weapon and armor rules of ABP are optional rather than mandatory. A character may attune to any weapon or armor to gain these bonuses, but they overlap with any bonuses the weapon or armor may already have. The prices for magic weapons and armors follow the standard cost progression (rather than the reduced cost in ABP).
The motivation behind these changes is similar to Tiered Gestalt: we want players to feel empowered to use different items than those most commonly used (often referred to as the 'Big Six'). Rather than rewarding players with twice the gold, we prefer to split the difference by giving some built-in bonuses.
Characters have two alignments in Ledge Campaigns: public and private. You public alignment is akin to your reputation - it's a reflection of how others judge you by your actions. Your private alignment is tied to your character's beliefs - why do they choose to take action? Your public alignment is known to other players and NPCs, while your private alignment should be kept between you and the GM. Over the course of the game, your public alignment will change in response to your character's actions (and how those actions are perceived), but your private alignment will only change in response to character development (when you've had a change of heart). It may be possible that your character doesn't even know his or her private alignment, but as a player you should.
Functionally, either alignment may be used to qualify for rules or options that depend on alignment. When it's your choice, you can decide which alignment applies in that case. When it's not your choice (such as when a Paladin smites you), they choose whether or not to apply your public or private alignment. Vigilantes and other characters that can create new personas can choose to gain an additional public or private alignment when they do so.
For example, if your public alignment is Lawful Good but your private alignment is Lawful Evil, you can still gain levels as a Paladin. If your public alignment ever changes, however, you'll become an Ex-Paladin. If you secretly cast an evil spell, you could not fall, as you can count your alignment (and any codes of conduct dependent on alignment) as though you were evil. The reverse could also be true: a tyrant could cast evil spells while continuing to progress as a Paladin so long as her beliefs were consistent with a Lawful Good alignment. At some point, she will have to come to terms with her actions, however.
Only characters that have both a good public and private alignment can be exalted (and take exalted options). Similarly, only publicly and privately evil characters can take vile options.
Players should expect that their public alignment will change frequently (as determined by the GM), but that their private alignment won't change without their consent.
Characters no longer need to roll for HP when they level up - they always receive the maximum amount of HP they could have rolled each level.
We'll be using the Fractional Base Bonuses rules. This will make multiclass and gestalt characters a bit easier to manage.
We'll be playing with the Background Skills rules with no changes. Make sure to track your background skill points separately from your adventuring skills!
The Pathfinder skill system remains relatively unchanged with a few additions to accommodate extra skills from D&D 3.5:
Instead of gaining +1 to any ability score every 4th level, characters now gain +1 to any two different ability scores every 4th level. You can't put both bonuses into the same ability score, but otherwise there are no limitations.
Class resources that would combine when multiclassing combine when gestalting. For example, power points, spell points, or essence from multiple sources would stack as normal. When using classes across editions that have functionally identical class resources that could conceivably combine, assume that they do. For example, essence and essentia are functionally the same, so they would combine into the same pool.
Any rule or option specific to a given setting or campaign can be reflavor to fit into a Ledge Campaign. Work with the GM to select an appropriate flavor for anything that you'd like to change in this way. This may allow for some prerequisites to change. Assume that deities, races, or other background prerequisites can be changed, but class or alignment requirements cannot.