From publisher blurb:
Ever wanted to have NPCs travel with your party, only to be discouraged by the extra time they add to combat? Or perhaps you want to have that one important NPC adventure with the players, but you want to avoid the infamous DMPC. Or maybe your players just woke up in a jail cell with 10 other NPCs that are all interesting, but keeping them all around is just too much to keep track of.
Fear not! The Companion System is here to solve all of your problems. With this simple system, you can easily track companion NPCs in an abstract way that keeps them relevant and interesting, but allows the PCs to remain front and center.
Originally designed to help deal with all of the NPCs in Out of the Abyss, the Companion System is an easy set of new rules that can be added to any adventure, even an ongoing one. It also includes optional rules for handling mounts, familiars, and ranger beasts as companions.
I did not include my Out of the Abyss companion cards in this document, opting instead for spoiler-free generic companions with art I’m allowed to use, but if you want them, see the comments below.