Secrets of Undeath: Lichdom

Through some means you've learned the secrets to becoming a Lich, and have completed the necessary ritual. This arduous process has transformed you and made you into a powerful undead. You gain the following benefits:

• Undead Nature - you do not require air, food, drink, or sleep.
• You are resistant to Cold, Lightning, and Necrotic damage.
• You are immune to the Charmed, Exhaustion, Frightened, Paralyzed and Poisoned conditions.
• You are immune to poison damage and Bludgeoning, Piercing and Slashing damage from non-magical attacks.
• You gain the Paralyzing Touch action. Make a melee spell attack that deals 3d6 cold damage to a target within range. If hit the target must succeed a Constitution saving throw equal to your spell save DC or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Limited Immortality.  When you die your mind and soul are drained from your corpse as it falls to dust. In 1d10 days your body reconstitutes next to your phylactery. Coalescing from glowing smoke that issues from the device. However, the phylactery requires soul sacrifices to maintain a working order. You must periodically feed souls to your phylactery to sustain the magic preserving your body and consciousness.

To do this, use the imprisonment spell. Instead of choosing one of the normal options of the spell, you use the spell to magically trap the target’s body and soul inside your phylactery. The phylactery must be on the same plane as you for the spell to work. The phylactery can hold only one creature at a time, and a dispel magic 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 begins to physically fall apart, and might eventually become a demilich.