You can never have enough variety of undead. This Codex gives a wide range of types and variations on commonly encountered undead and beefs them up with legendary actions or a bonus action, reaction or special ability to add another layer of danger. I liked Zoroth the Lich, the Reanimated Colossus and the ghoul hounds (large size) are cool though a pack of them all with legendary actions may be a bit tough? I will make a medium size version of these without the legendary actions and have the one in this pdf as an alpha pack leader. All the stat-blocks give enough that I can work with to fit into an adventure. I noticed an error on the Sanguine Shade and the designer quickly amended it; thank you. Why a 4 and not a 5? If the codex expanded with Lair Actions, plot hooks, back story, flavour text for example then I would give a 5. Some abilities repeat in some fashion but I appreciate the challenge of trying to make something fresh on old undead powers like life drain, horror screams and raising or controlling undead. The art is evocative and chilling to spark the imagination. I am definitely inspired to try my hand at something new when it comes to undead. I would recommend this codex if your looking for new undead to use and to refresh your imagination when writing an adventure that requires a cool undead boss.