Libris Mortis is all about undead -- their abilities, how to fight them, how to improve them, and how best to use them in your campaign. It's a big book with a lot of material that can add depth to your campaign and make your role as DM easier. Below are ten reasons why this book is a great tool for DMs.

10. New Feats for Monsters: Libris Mortis offers piles of new feats that power up undead or change their abilities in some way. For example, the Necrotic Reserve feat lets an undead creature that bestows negative levels or deals ability damage or ability drain store some of the energy taken from its victims. This stored energy can keep the creature alive for a short time if it ever takes enough damage to reduce it to 0 or fewer hit points.

9. Cults, Cults, Cults: The various cults of undeath detailed in Libris Mortis can provide lots of new villains for your PCs to face. The Minions of the Skull, for example, worship undead beings and view undeath as the way to achieve immortality. Each cult description comes complete with origins, goals, ideas for incorporating it into your campaign, and best of all, full statistics for a sample cultist.

8. Templated Undead Samples: Need some undead NPCs fast? Libris Mortis presents full statistics for five creatures using each of the undead templates in the Monster Manual. That's five sample ghosts, liches, and vampires, each complete with backstory and complete game statistics. More than ten skeleton creatures of various sizes and more than ten zombies are also featured, including strange applications such as the glabrezu skeleton and the hound archon zombie.

7. Incorporeality Clarified: A line-by-line breakdown of the definition of incorporeality explains and clarifies each aspect of this powerful and confusing ability. This section also suggests tactics that complement incorporeality, such as hiding in the same square as another creature, or living at the bottom of a waterfall so as to limit the enemy's mobility.

6. New Spells and Magic Items: Libris Mortis offers a wide variety of new spells and magic items that augment undead abilities. For example, cyst spells allow the caster do strange and horrible things to a creature he has implanted with a cyst of necrotic tissue, and the necrotic focus weapon ability allows a vampire or similar undead to employ its ability drain or energy drain through a melee weapon.

5. Prestige Classes: Libris Mortis details five prestige classes for evil characters, plus four other prestige classes specifically for undead. The death's chosen is a living creature that chooses to pledge service to a powerful undead, and the master vampire can control dozens of spawn and enhance some of them beyond their normal capabilities. New 3.5-compatible versions of the pale master and true necromancer are also presented.

4. Variant Template Abilities for Undead: Ghosts, liches, skeletons, vampires, and zombies all get alternate sets of abilities to keep your book-memorizing players on their toes. For example, vicious skeletons gain mindless pleasure from disemboweling opponents with their oversized claws, psychic vampires attack Wisdom instead of Constitution, and hunter zombies track by scent.

3. Monster Classes for Undead: Do you want to use a ghast, ghoul, mohrg, mummy, vampire spawn, or wight against lower-level PCs without killing the entire party? Just use a lower-level version of the monster instead of the fully powered one. If you liked the monster classes in Savage Species, you'll love these!

2. Undead Tactics: Libris Mortis offers tactics for all the undead presented in the Monster Manual. These combat techniques utilize each monster's resources in the most efficient way, enabling it to take out enemies as fast as possible.

1. New Undead: Looking for new undead monsters at various CRs? Look no further! Imagine your PCs' surprise when a skulking cyst bursts out of a matured necrotic cyst. And they'll definitely have to rethink their tactics when facing an undead with the swarm-shifter template when it becomes a swarm of beetles, leeches, very small undead creatures -- or even stranger objects, such as sand or undead body parts.