A note, from Link, before we begin. The lore here basically defines and summarizes the Undead race. To view more detailed Undead lore, lore of the specific sub-types, refer to the bottom of the page.
Credits to Baba for the creation of all material to follow.
A note before we begin. All undead are bodies that have died and are then reanimated by unholy means (Modes of undead resurrection at the end). This includes constructs made from biomass, body parts or unholy plagues. A person or creature resurrected by holy and proper means is not an undead and is considered resurrected. An undead can undergo a holy purification of some sort to be accepted by society and the light, losing the monstrous desire to kill and even regaining a soul. The disgusting necrotic magic and diseases within an undead are then cleansed from the form and replaced with holy light.
The light and the dark. Holy and unholy. They seem like strange concepts. You may view them any way you’d like, but they have no relation to religion what so ever! These terms simply describe how one uses Celestial and Eclipse magic. Any terms referring to “Holy” simply mean the use of magic for good purposes and to propel spiritual health. Unholy means the wicked, twisted use of magic that goes against nature and harms others. Eclipse and celestial are not forever deemed unholy and holy, respectively. Light and dark magic are not the same as celestial or eclipse magic and are also not solely holy or unholy, respectively. Light and dark are a part of nature and therefore both celestial and eclipse magic practitioners can make use of them.
Different types of magic affect undead in different ways. Light magic harms undead, but a necromancer, if using unholy light, can make their undead immune. Dark magic can be used to heal undead. Light magic, when used to heal undead will always be painful, but will heal the undead none the less. Unholy magic is always used to resurrect and create undead. If the resurgence magic is holy then they are simply resurrected. Holy resurgence magic cannot work on a corpse with a certain level of decay as it would take great power and time. A body, when being resurrected with holy resurgence magic, has its cells literally re-crafted from surrounding matter and atoms. The matter and atoms used in holy resurgence is often simple dust or dirt, so as to not harm the area around the corpse.
An undead can acquire any level of flesh regeneration, but it will take a combination of magic and science unless the magic restoration is given by a person with immense creation abilities. Undead are harmed by normal healing spells. The wound will be healed but it causes much pain to the undead. Undead wounds can only be healed by a shadow priest/healer/cleric, unholy healing potion or by their resurecter. A player may say they are undead when resurrected by holy means (such as Dara resurrecting us) but is not technically an undead and anti-undead magic will not harm them. All real undead are subject to anti-undead magic, but that magic must be specified as such. Some undead are able to withstand normal holy, celestial, or light magic.
There are different types of Undead. You may be asking “aren't all undead the same mindless, rotting creatures?” No. The different types may have different modes of undead resurrection, skills, levels of knowledge, genetic makeup, appearance/build/structure, magic auras, soul/spirit and weaknesses. Now, let's get down to business, shall we?