Undead

Oblivion. All undead creatures are animated by a cosmic force known as oblivion. This demiurge attempts to erode what already exists, particularly things already succumbing to the late stages of entropy. 

Hollowing. Whenever a living creature becomes undead, the power of oblivion fills its mind. Strong-willed creatures can resist this impulse for a time, but it inevitably causes madness and a desire to either go on a rampage or withdraw from the world and enter torpor. This is how living minds reconcile oblivion's cosmic imperative: to return all of reality to a state of primordialism. In mystic subcultures, this effect is known as the Hollowing. 

Phylacteries. Powerful undead creatures can protect their souls from the hollowing by placing them in an enchanted reliquary. This protects the soul from oblivion's touch and allows the creature to retain its intellect for centuries. If an undead creature with a phylactery is destroyed, it possesses a new corpse within 1 kilometer of its phylactery 1d10 days later. 

Nightsong. Undead creatures that operate together in large numbers become connected by a gestalt hivemind known as the nightsong. Because of this, telepathic creatures can “sense” large numbers of the undead by the eerie siren call they give off. Powerful undead with the ability to command lesser creatures do so by “singing,” and necromancers learn to wrangle undead by broadcasting their artificial version of the nightsong. Some believe it to be the haunting, seductive, and predatory call of entropy. What is known is that when thousands of undead gather together, their evil psychic “whalesong” can be heard for miles by telepathically sensitive creatures. 

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Shamblers. The most basic form of undead. They can be created by necromantic spells, proximity to mystic corruption from the lower planes, ancient curses, etc. There are two basic types; skeletons are faster and resistant to piercing damage, while zombies have more health and are resistant to crushing damage. Some shamblers have the persistent trait, reforming 1d6 minutes after destruction unless the animating magic is dispelled or their remains are scattered or destroyed. Unless commanded by a more powerful sentient undead, these creatures remain dormant but animate to attack targets that get too close. 

Oreks. Also known as apocalypse zombies, oreks are corpses possessed by malign spirits. Unlike shamblers, they possess a low intelligence and can be identified by their leering visage and/or mutations concurrent with the nature of the possessing spirit. Although powerful and intelligent specimens are scarce, they do exist. Oreks are greatly feared for their ability to stalk, climb, mob, and run after victims with animal cunning. Humanoids they kill rise the next nightfall as spawn, and some rare strains carry a magical disease that can be communicated via a bite. 

Ghouls. Also known as necrophages (eaters of the dead), ghouls are corpses consumed by a supernatural hunger for flesh and blood. A ghoul that successfully kills and devours multiple sentient humanoids grows more robust and more intelligent, becoming progressively more dangerous until it undergoes a metaphysical transformation into a ghast. 

Wights. Wights are sentient skeletal undead with a strong connection to the Great Void. They can be identified by the shadow stuff that suffuses their bones and equipment, making them more resilient than lesser corporeal undead. A wights intelligence tends to vary; some are nearly mindless while others retain their personality. The touch of a wight saps life force from living creatures, and this draining effect can be communicated through their melee weapons. Sometimes wights are created by the same circumstances as shamblers. If properly motivated, wights are capable of speaking. 

Draugr. Fully sentient and very dangerous, Draugr are undead and retain all the skills and knowledge they have held in life. They are usually created by potent necromancy or some sort of curse and have the innate ability to command unintelligent undead in their vicinity unless they are already enslaved to another being's will. Necromancers who create draugr must mystically bind them with a symbol of oppression to ensure total obedience (shackles, sewing the mouth shut, a brand, or similar). If the symbol of oppression is ever destroyed, the draugr becomes free-willed. Unscrupulous individuals may also use ritecraft or dark pacts to transform themselves into free-willed draugr to evade actual death. If you need to create a fully self-aware undead humanoid but do not wish to make it something truly extraordinary like a vampire, liche, or dullahan, this is the template to use. 

Dullahan. Only the mightiest of warriors and rogues can rise from death as a Dullahan, and the appearance of one always indicates that dark gods, arch-necromancers, cursed artifacts, or similar powers are involved. The defining element of a dullahans curse is that it is missing either its head or its heart. The creature can manifest a spectral voice when a headless dullahan wishes to communicate. The missing organ is the entity's phylactery, so only by destroying it can the creature be destroyed. Whoever holds a dullahan's phylactery can control the creature, and dullahans may be created against their will through ritual. An unwilling dullahan that gains possession of its phylactery will be laid to rest. A dullahan that approves of its undead status will hide its phylactery well to protect itself. 

Liche. A liche is a powerful spell caster who has evaded death by placing their soul into an object known as a phylactery. The resulting undead creature retains full awareness and function, sustained by dark magical energies that greatly amplify its powers. A lich can only be destroyed through the destruction of its phylactery. The process of becoming a lich requires several unsavory acts of destruction and sacrifice that are incompatible with a good alignment. Despite the power and immortality lichdom provides, mortal minds do not handle eternity well. The oldest liches inevitably go insane, experiencing a form of profound mental exhaustion that compels them to self-isolate and then sleep away the ages until events compel them to rise and take action briefly. 

Ghost. A ghost is the disembodied soul of a once-living creature that failed to transmigrate after death due to dark magic, curse, or sheer force of will. All ghosts can dematerialize, spreading their essence over an area of variable size and entering a dreaming fugue state where they are only vaguely aware of nearby events. Ghosts tend to manifest in response to some triggering event, or when compelled to do so by magical means. Not all ghosts possess the same level of power or self-awareness. Haunts are psychic echoes of their former selves with little to no power, while wraiths are self-aware spirits capable of combat or conversation. Ghosts warped by darkness become specters: predatory spirits that develop monstrous traits and thirst for life force. 

Vampire. Perhaps the most famous of all undead, a vampire is an undead humanoid cursed with a thirst for blood. The cosmos has dozens of vampire bloodlines, each granting different powers and affinities. As vampires age they grow more intelligent and develop greater self-control, allowing them to blend into civilization more effectively. While not blatantly malicious, the transformation into a vampire fills a subject with a thirst for blood and the impulse to regard mortals as prey. Even if their predations are carefully moderated or transactional, this causes them to grow callous and unfeeling over time. 

Weaknesses. All vampires have certain weaknesses in common; they are burned by sunlight, they find strongly presented holy symbols blinding, they stop regenerating and are forced into torpor if staked through the heart, they do not like fire, and they are dangerously allergic to some form of local plant. 

Abilities. Every vampire bloodline has unique powers to help them hunt mortals and avoid detection. In keeping with their role as predatory parasites, vampires are often attractive and can easily masquerade as living humanoids. Certain vampire bloodlines originating in the lower planes are simply monstrous, however. 
Reproduction. Vampires reproduce by draining a humanoid creature of blood to the point of death, then forcing the dying creature to consume their blood. This process is highly traumatic for both the vampire and the victim, so it is never done on a whim. 

Bloodspawn. If a vampire drains a mortal creature of all its blood, that creature becomes a bloodspawn under the vampire’s control the following night. Bloodspawn are oreks with vampiric physical traits and a thirst for blood.