The book explains everything you need to play, including basic rules, weapon keywords, phases, actions, terrain for three separate Killzones (the vertical Volkus, watery Bheta-Decima, and confined Gallowdark), and provides two Mission Packs (the classic head-to-head Preliminary Ops pack and the new Joint Ops pack in which one or more players can play against the game itself, including full behaviours for a range of automatically controlled enemies known as Non-Player Operatives or NPOs).