From publisher blurb: Introducing the Monstrous Monograph, a growing collection of monsters with which Fifth Edition game masters can challenge their players. Each volume of the Monstrous Monograph presents a handful of creatures of a given monster type. Grow your collection a few monsters at a time for far less than the price of your morning coffee! Monstrous Monograph: Undead Vol. I contains four new monster, and six statblocks: The CR 3 Alley Ghast and CR 6 Alley Ghast Survivor are a variant form of ghast which possess far greater cunning. They dwell in hidden corners of towns and cities, emerging at night to prey on the vulnerable and forgotten. Alley ghasts prefer a solitary existence but in times when prey is bountiful they sometimes emerge as the leader of local ghoul packs. When a ghoul feasts on a recent battlefield or from a mass grave, they can evolved into the CR 7 Battlegorged Ghoul. The spirits of all the restless dead whose bodies they consumed are absorbed into them, and the battlegorged ghoul can regurgitate them as specters which must do its bidding. The CR 4 Bone Keeper is a type of skeleton created to guard necromancers and other powerful undead. A skeletal torso, Bone Keepers float behind the creature they're protecting and use their elongated arms to provide cover to their ward. The CR 2 Lifeleech Skeleton is a more powerful variant of skeleton that can drain life energy with a touch, and emits a necrotic aura that is deadly to living creatures it approaches.