Reworking the 3-Pillars of Experience to add a new Pillar, Character.
The addition would be for exploring characters backgrounds, or otherwise enhancing the experience with your character.
In short, ever level takes 100XP, XP gained is based on events and actions taken that are centered around the 3 pillars of Exploration, Socialization, and Combat. Adding the 4th Pillar of Character to try and promote character interaction.
Exploring and Expressing your character, exploring others as well.
Conversing and exploring another characters background provides experience for the character digging into their background. Exploration of Background is disconnected from character tiers, simply because backgrounds don't increase in difficulty with character levels.
5XP: Start and hold a conversation about someones past that allows them to reveal a new part of their backstory.
+5XP: Conversation contains a dramatic reveal or poignant accusation, explores a conflict or disagreement between characters, or otherwise carries some meaningful weight for all involved. All characters involved in the conversation gain 5XP.
5-10XP: Discover a secret part of another characters background.
10-20XP: Discover a part of your background you didn't know.
Completing personal goals related to your characters background appropriate to your tier earns you 10 XP, plus an additional 10 XP for each tier above your current tier. You gain half XP for Character Goals below your tier. This needs to be a personal goal, and not simply a quest given to the party.
Tier 1: Complete character goal that effects a small town or village.
Tier 2: Complete character goal that effects a kingdom.
Tier 3: Complete character goal that effects the world.
Tier 4: Complete character goal that effects the planes.
Playing a character trait that risks the success of another Pillar grants an additional 2XP if it's at your current Tier, plus an additional 2XP for each Tier above your current tier. Because it's tied to another action, it only grants XP if the action taken produces XP.
Tier 1: Succeed or Fail another Tier 1 Pillar because of a Character Trait.
Tier 2: Succeed or Fail another Tier 2 Pillar because of a Character Trait.
Tier 3: Succeed or Fail another Tier 3 Pillar because of a Character Trait.
Tier 4: Succeed or Fail another Tier 4 Pillar because of a Character Trait.
Example: A Tier 1 combat involves spiders, character willingly takes the frightened status for the entire combat. The group defeats them despite the characters drawback, gains XP from combat, and then that character gains an extra 2XP for playing to their fear of spiders.