Arcanus Eternum

As the study of magic has evolved, the idea of using magic to not only extend one's life but to ensure it never ends has become a popular avenue of study. Over time, methods to achieve life everlasting have been developed, each one utilising a different schools of magic. These methods are known as the Arcanus Eternum and those who have exploited them as Arcanus Eternals. While magical immortality is appealing, it is believed that it inevitably comes at the cost of the lives of others, even if the seekers intentions are pure.
Many actively hunt those seeking to achieve Arcanus Eternum. The Watchful Order sees them as abominations that risk inviting the wrath of those entities or organisations that would associate them with all arcane practitioners. Servants of Kelemvor hunt them down mercilessly.
There are eight varieties of Arcanus Eternum, each one resulting in a different Eternal, utilizing a different school of magic and associated with a different vice.

Lich

Necromancy - Sloth

The oldest and most commonly known of the Arcanus Eternum, a Lich has bound its soul into an object known as a phylactery. A Lich rarely worries about being destroyed, as its phylactery will always return it to some form of unlife. With this guarantee, most Liches are patient creatures and can plot revenge on its own time, even on its slayer’s progeny.

Sarg

Abjuration - Gluttony

A leviathan in a puzzle. A Sarg has banished itself to its own private pocket dimension between the planes, nestled so deep into a maze of magical wards and safeguards that not even the god of death can reach it. A Sarg sustains itself by siphoning the souls of the dead into its waiting maw, trapping them within. Sargs are of the greatest danger to souls passing into the afterlife and sometimes those traveling between planes.

Tulpa

Divination - Despair

A Hadrach avoids death by sheer degree of prescience, witnessing the extent of time and reality around it by understanding in full the suffering of existence. A Hadrach sees and knows it's destiny and must simply follow the path that keeps it alive. In this lies a Hadrach's curse, for it is akin to a puppet who can see its strings. Indeed, by becoming a Hadrach, one inevitably learns the certain terms of one's own death, a revelation that drives many to madness.

Hadrach

Divination - Despair

A Hadrach avoids death by sheer degree of prescience, witnessing the extent of time and reality around it by understanding in full the suffering of existence. A Hadrach sees and knows it's destiny and must simply follow the path that keeps it alive. In this lies a Hadrach's curse, for it is akin to a puppet who can see its strings. Indeed, by becoming a Hadrach, one inevitably learns the certain terms of one's own death, a revelation that drives many to madness.

Regaia

Enchantment - Lust

A thought, an infection. A Regaia exists as a possessing influence, spreading into the minds of creatures, taking them as host bodies and overwriting their consciousnesses with its own. As long as it remains an idea in the mind's of others, it can always spread its essence. A Regaia can quietly overtake villages or entire towns in the span of weeks, replacing the minds of their inhabitants with its own.

Makt

Evocation - Wrath

Makt manifest in a myriad of forms; an iron golem containing an elemental furnace which constantly reforges its body, a glacial titan whose wounds freeze over in the blink of an eye. Makt are those who have relinquished their bodies, instead sustaining a new form through raw elemental might. A Makt is unique in that it draws constantly upon the arcane, always channeling a torrent of magic to fuel itself. Makt are particularly dangerous to mages as when they grow powerful enough they begin to siphon magical energy from around them, rendering spellcasting difficult, if not impossible.

Gespen

Illusion - Pride

By weaving complex illusions a Gespen becomes a living dream. Gespen's lack a physical form, instead they spread over an area, consuming reality. A Gespen sustains itself on the belief of others, feeding best upon a long life lived under the spell of its illusion. Within its bounds the Gespen shapes reality as it sees fit, manifesting itself with simulacrums and shaping the landscape to fool those within. The Gespen hides its death under multiple layers of illusions and can only be slain by uncovering this truth within the heart of its realm.

Sharrkyth

Transmutation - Greed

A Sharrkyth prolongs its life by successively polymorphing itself, changing form each time death approaches. Each layer of transformation brings greater instability until the Sharrkyth has become a horror of constantly shifting form. It must absorb entities into itself to avoid reverting to it's true form and exists as an eternal cancer. A Sharrkyth only sustains one form long enough to draw in prey and merge it into itself.