Brother's Bile

Legendary Resistance (3/Day). If one of The Brother's Bile fails a saving throw, it can choose to succeed instead.

Bond Of Blood. While within 10 ft. from each other, they gain resistance to all forms of damage. 

Spellcasting. The Brother's Bile is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The Brother's has the following spells prepared:

Cantrips (at will): mage hand, Shocking Grasp, ray of frost

1st level (4 slots): Chromatic Orb, magic missile, shield, thunderwave, Ray of Sickness

2nd level (3 slots): acid arrow, Maximilian’s Earthen Grasp, invisibility, mirror image

3rd level (3 slots): Fear, counterspell, dispel magic, fireball

4th level (3 slots): blight, dimension door

Turn Resistance. The Brother's Bile has advantage on saving throws against any effect that turns undead.

Combined Spellcasting. The Brothers are linked regardless of distance or even plane, due to this they share the same hit points, if one suffers damage the other does as well. However if one Brother casts a spell, the other casts the same spell regardless of distance apart or initiative.

Consuming Touch. Melee Spell Attack: +12 to hit, reach 5 ft., one creature. Hit: 10 (3d6) Psychic damage. The target must succeed on a DC 18 Constitution saving throw or be paralyzed for 1 minute. While paralyzed, the target is slowly being consumed by the brother. While in this state, the player is treated as Unconscious, as they are slowly being consumed. If reduced to zero hit points, a character is turned into a Brother Vile, healing the Brother's to half health. The target can repeat the saving throw at the end of each of its turns, taking the 3d6 Psychic damage on end of their turns until a success,  to which the effect ends on a success save.

The lich can take 3 legendary actions, choosing from the options below. Only one legendary action option 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.

Cantrip. The Brother's Vile casts a cantrip.

Consuming Touch (Costs 2 Actions). The Brother's uses its Consuming Touch.

Frightening Gaze (Costs 2 Actions). The Brother's Bile fixes their gaze on two creatures it can see within 20 feet of it. The target must succeed on a DC 18 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to the Brother's gaze for the next 24 hours.