Planeshift Tarkir
Spellcasting. The lich casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 18):
Legendary Resistance (3/Day). If the lich fails a saving throw, it can choose to succeed instead.
Regeneration. The lich regains 10 hit points at the start of its turn. If the lich takes fire or radiant damage, this trait doesn't function at the start of the lich's next turn. The lich dies only if it starts its turn with 0 hit points and doesn't regenerate.
Turn Resistance. The lich has advantage on saving throws against any effect that turns undead.
Undead Fortitude. If damage reduces the lich to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the lich drops to 1 hit point instead.
Multiattack. The lich makes three Arcane Burst or Bone Staff attacks.
Arcane Burst. Ranged Spell Attack: +10 to hit, range 60 ft., one target. Hit: 27 (5d8 + 5) necrotic damage.
Bone Staff. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) bludgeoning damage plus 21 (6d6) necrotic damage.
Feed on Death (1/Turn). When the lich kills a creature with necrotic damage, the lich regains 9 (2d8) hit points.
The lich can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The lich regains spent legendary actions at the start of its turn.