The D&D Gamma World game comes with an introduction adventure that takes the characters from level 1 to level 3, while demonstrating how the game works. This is good!
The adventure is designed for 5 PCs and doesn’t give guidelines on how to properly scale the encounters for different numbers of players. This is not good!
Here are two different articles I wrote that give you options for running “Steading of the Iron King” with fewer than (or more than!) five player characters.
Scaling the Adventure
To adjust each encounter for a variable number of players, follow these general guidelines. For more than six players, repeat the instructions for six players for each additional player. See page 92 of the D&D Gamma World rulebook for information on building level-appropriate encounters.
A few of these adjusted encounters push up against the next higher level of encounter. That’s okay as encounter levels are guidelines not strict rules, but you may want to further adjust some of the monsters or provide players
with extra assistance if they are having difficulties. For example, one of the terrain features might fail to function as written (such as The Machine in encounter 3).
Each encounter lists the monsters and hazards as written up in the adventure for five players, and then offers suggested changes to make to provide a challenge of the approximate difficult and general feel of the encounter for fewer players.
Unlike player characters, companion characters are relatively stable within their niches in Gamma Terra. Companion characters do not receive Alpha Mutation cards and never experience Alpha Flux events. They are also unable to use Omega Tech items and do not draw Omega Tech cards.
Companion characters can use the second wind action as player characters can, and like player characters, they heal to maximum hit points after a short or extended rest. They die at their negative bloodied values, not 0 hit points.
Companion characters don’t use ammo; they never have to worry about running out if they fire guns, and they can’t replenish a player character’s supply by giving ammunition to them. A companion character who comes with equipment can be given other, similar equipment to use, but the game mechanics for the companion’s
powers will remain the same. For example, if a companion uses a short sword and is given a yield sign (a heavy two-handed weapon), the companion’s attack will still function as if he were using the short sword.
This supplement includes the companions Roberta the Rebuilt Robot, Milton the Paranoid Dabber, and Enik the Time-Lost Sleeth.