Companions are like magic items from a mechanical point of view. A character finds one, attunes to it, and gets some kind of benefit. Beyond that it’s just assumed that you have a dog or whatever following you around, but it’s not a major character in the story. If it were, then it would be a PC (which I’ll cover later). Asking your dog to run up and attack a demon is not part of this design. Also a companion is not a familiar, and does not gain any magical abilities beyond what a normal animal of its type could do. Companions can be used as an alternative to magic items, for example in a low magic campaign, or alongside magic items. If one character finds a magic shield, and another gains a wolf companion, they both gained some benefit. Companions have rarity, just like magic items, including common, uncommon, rare, very rare, and legendary. Common companions include normal animals, such as a cat, dog, mouse, or sparrow. Sheepdog Companion (dog), common A sheepdog is ...