Bill Cipher

Regeneration. Each round, Bill Cipher can choose to heal 5d10 + 22 instead of doing his turn.

Creation. Bill Cipher can cast Creation at will and the duration of whatever thing he creates is infinite and he can make it any size he wants. If it has a volume bigger then 100ft then he must take a Short Rest before he can use this feature again. If it has a volume bigger then 1000ft he must take a Long Rest before using the feature.

Time Stop. Bill Cipher can make time stop in a 100 mile radius for everything except people. He can have it going for as long as he wants but he has to take a Long Rest at least once per day.

Eye Weakness. If Bill Cipher is hit in the eye the damage is doubled and if he is hit in the eye with radiant damage it's quadrupled. He is also Blinded for three rounds and can't regenerate for that time.

Mind Door. Bill Cipher can enter any sentient beings mind when they are asleep. If Bill try’s to enter someone’s mind, the being has to roll a wisdom saving throw the DC being 20. On a failed save, Bill enters the beings mind and is able to view there memory’s and modify there dreams. On a successful save, Bill cannot view the beings memory’s but Bill can still modify there dreams.

If there is something preventing Bill from accessing someone’s mind, the being gets advantage on the saving throw. On a failed save, Bill can only modify dreams but he cannot view memory’s. On a successful save, Bill cannot access the beings mind.

Spellcasting. Bill Cipher is a ∞-level spellcaster. Its spellcasting ability is Intelligence (spell save DC #, +# to hit with spell attacks). Bill has the following Bard spells prepared:

Cantrips (at will): [Mind Sliver], [Vicious Mockery] 

1st level (15 slots): [Charm Person], [Sleep], [Illusory Script]

2nd level (15 slots): [Hold Person], [Suggestion], [Tasha's Mind Whip], [Mirror Image], [Phantasmal Force]

3rd level (13 slots): [Catnap], [Enemies Abound], [Fear], [Major Image]

4th level (11 slots): [Charm Monster], [Confusion], [Dominate Beast], [Compulsion], [Hallucinatory Terrain], [Phantasmal Killer]

5th level (9 slots): [Dominate Person], [Hold Monster], [Synaptic Static], [Geas], [Modify Memory], [Dream], [Mislead], [Seeming]

6th level (7 slots): [Mass Suggestion], [Otto's Irresistible Dance], [Mental Prison], [Programmed Illusion]

7th level (5 slots): [Power Word Pain], [Mirage Arcane], [Project Image], [Simulacrum]

8th level (5 slots): [Dominate Monster], [Power Word Stun], [Feeblemind]

9th level (3 slots): [Power Word Kill], [Psychic Scream], [Weird]

Multiattack. Bill Cipher can use Punch two times and one Eye Beam.

Punch. Melee Weapon Attack: +22 to hit, reach 20 ft., 1 target. Hit: 68 (10d12 + 22) bludgeoning damage. 

Eye Beam (Recharge: 6). Ranged Weapon Attack: +22 to hit, range ∞/∞ ft., ∞ target. Hit: 83 (12d12 + 22) fire damage plus an extra (6d12) necrotic damage.

Bill Cipher gets ten legendary actions and is refilled after a Long Rest.

Giant Fist Smash (Costs 2 Actions). On the first action, Bill Cipher rears his fist behind him growing to a large size. On the second, his fist slams down and everybody in the 20 by 20ft circular area of the targeted spot must make a dexterity saving throw (DC: 22.) On a failed save the targets must take (20d12 + 22) bludgeoning damage and take half on a success.

Mega Bill (Costs 5 Actions). The damage of every attack is doubled and Bill's size changes to Gargantuan for a minute.