A recent thread here inspired me to finish writing up my rules for higher level characters.
While the D&D Gamma World game only allows character advancement to level 10, the related Dungeons & Dragons game goes up to level 30 in three tiers: Heroics (1 to 10), Paragon (11 to 20), and Epic (21 to 30).
These house rules expand D&D Gamma World to level 20 by introducing the Uber Tier (11 to 20).
Uber tier characters:
- Continue to advance in level as before, gaining 5 hit points per level, as well as level-dependent increases to attacks.
- Gain permanent Alpha Mutations which don't change at the end of rests or due to Alpha Flux.
- Gain additional Uber Feature choices while advancing in level.
- Continue to gain Vocation Feats. Uber tier characters invariably have multiple vocations.
- Do additional damage with basic attacks.
- Pick a Survivor Path which gives them access to Survivor Path powers – novice, utility, and expert powers that aren't based directly on their origins.
- Gain Survivor Path traits including critical hit benefits at 13th and 17th levels.
- Increase one ability score – based on Survivor Path – at 12th level and again at 18th level.