TEXT: The Path to Lichdom
  T
  his is my attempt at providing lichdom to
  players via epic boons. I don't intend to
  comment on what kind of quests a PC would
  need to undertake to earn these boons; that's
  setting-dependent anyway. The idea is that you
  need to collect several boons before you can
  call yourself a lich, which represents the fact
  that the 'average' lich is ancient in years and vastly more
  experienced than even a 20th level PC should be. Without
  further ado, here are the boons. Let me know what you think!
  Epic Boons
  Boon of Epic Necromancy
  Prerequisites.
  Able to cast 9th level spells.
  Know at least one necromancy spell
  You gain one 10th level spell slot that can only be used to
  cast necromancy spells of 9th level or lower. When cast at
  10th level, the spell create undead allows you to create or
  reassert control over 8 ghouls, 4 ghasts, wights or mummies,
  or 2 revenants or wraiths.
  Boon of Lichdom
  Prerequisites.
  Boon of epic necromancy.
  Boon of unspeakable knowledge.
  Access to the spell Imprisonment.
  You perform a terrible ritual to become an immortal,
  undead abomination. You can no longer die of old age, though
  your flesh continues to age unless you take steps to preserve
  it. Your creature type changes to undead, you can no longer
  benefit from healing magic and you don't require air, food,
  drink or sleep. You are immune to the charmed, exhausted,
  paralyzed and poisoned conditions. Finally, you gain a
  phylactery (see below), which enables you to regenerate your
  body even if it is destroyed.
  
  Boon of Mastery Over Death
  Prerequisites.
  Boon of lichdom
  Years of undeath and layer upon layer of long-lasting
  abjurations have hardened your physical form. Your armour
  class is equal to 14 + your dexterity modifier, you have
  advantage on saving throws against any effects that turn
  undead and you are immune to poison damage and
  bludgeoning, piercing and slashing damage from nonmagical
  weapons.
  Boon of Unspeakable Knowledge
  Prerequisite.
  Non-good alignment.
  Able to cast 9th level spells
  Having unraveled the secrets of lichdom, you gain the
  ability to disrupt the life energy of other creatures with your
  touch. Your unarmed strikes now deal 3d6 cold damage and
  you may use your spellcasting ability instead of Strength for
  the attack rolls. Furthermore, you may choose to either force
  a target you hit with an unarmed strike to make a
  Constitution saving throw against your spell save DC or be
  paralysed for one minute (the target can repeat the saving
  throw at the end of each of its turns, ending the effect on
  itself on a success), or drain the target's life, gaining
  temporary hit points equal to the damage dealt.
  New Magic Item
  Phylactery
  Wondrous item, legendary (requires attunement by a lich)
  A phylactery is a small object, usually a locket or box, that
  houses a lich's soul. If a lich is reduced to 0 hit points, their
  body crumbles to dust but their will and mind escape to the
  phylactery. After 1d4+1 days, a new body for the lich
  coalesces as near to the phylactery as possible. The new body
  is identical in every way to the one that was destroyed.
  However, the lich must feed souls to its phylactery to
  sustain the magic preserving its body and consciousness. It
  does this using the imprisonment spell to magically trap the
  target's body and soul inside its phylactery. The phylactery
  must be on the same plane as the lich for the spell to work. A
  lich's phylactery can hold only one creature at a time, and a
  dispel magic spell cast as a 9th-level spell upon the phylactery
  releases any creature imprisoned within it. A creature
  imprisoned in the phylactery for 24 hours is consumed and
  destroyed utterly, whereupon nothing short of divine
  intervention can restore it to life.
  A lich that fails or forgets to maintain its body with
  sacrificed souls (at least one soul every ten days) begins to
  physically fall apart, taking 10d10 radiant damage at the end
  of the tenth day and being unable to recover hit points until a
  soul is fed to the phylactery, and might eventually become a
  demilich if it does not feed its phylactery for a year and a day.
  Every phylactery has a unique weakness that allows it to be
  destroyed. Determine this weakness by rolling on the table
  below or choosing your own.
  d10
  The phylactery can be destroyed by
  1
  Casting it into an active volcano
  2
  Submerging it in holy water for 24 hours
  3
  Smashing it with a weapon of legendary rarity
  4
  Opening it with a specific key
  5
  Taking it to Mount Celestia
  6
  Solving a puzzle-lock on the item
  7
  Performing a 1-hour ritual known only to the creator
  8
  Saying a secret passphrase
  9
  Playing it a certain song
  10
  Bathing it in the blood of a demon
  
SOURCE: textdata/thevault/Dungeons & Dragons [multi]/5th Edition (5e)/3rd Party/Mage Hand Press/Non-Published/Path to Lichdom.pdf