From publisher blurb:
The D&D Dungeon Master's Guide 2 introduced the concept of monster themes groups of statistics that can be used to flavor “stock” monsters to – give thematic unity to an encounter.
You can use the concept of monster themes to adapt D&D monsters from various sources such as the – D&D Essentials Monster Vault – for use in your D&D Gamma World game.
Choose an appropriate theme for the monsters you want to use, and then select one to three powers or traits from the list for that theme.
Here are three themes you can use in your campaign: cyborg, radioactive, and alien.