From publisher blurb:
This is the story of two kids, Bryan and Lilly, and their robot HK in the apocalypse on a quest to find their family. Along the way, they'll defend their home from bandits and mutants, befriend aliens and robots, and learn about the great big world outside their colony. They call it The Exterior.
The Gammapedia is HK's reference manual. It features datafiles on everything the kids encounter and plenty of critters they haven't discovered yet. It features 10 different alien species, 11 androids, 10 dragons, 7 fey, 16 different humanoid species, 17 kinds of giant and deadly insects, 24 killer plants, 37 robots, and a dizzying variety of mutants – over 220 in total! Each entry is fully illustrated with an accompanying graphic to demonstrate scale.
This PDF has a bookmarked table of contents with monsters linked by challenge rating. Challenge ratings range from 0 to 28.