Spellcasting. Angmar is a 20th level spellcaster. His spellcasting ability is Charisma (spell save DC 20, +10 to hit with spell attacks). Angmar has the following spells prepared:
1st level (4 slots): absorb elements, shield
2nd level (3 slots): blindness/deafness, heat metal
3rd level (3 slots): fireball, lightning bolt
4th level (3 slots): dimension door, [Tooltip Not Found]
5th level (3 slots): dominate person, synaptic static
6th level (2 slots): disintegrate, harm
7th level (2 slots): crown of stars, finger of death
8th level (1 slot): abi-dalzim's horrid wilting
9th level (1 slot): time ravage

Regeneration. Angmar regains 30 hit points at the start of its turn if it has at least 1 hit point and isn’t in sunlight or running water. If Angmar takes radiant damage or damage from holy water, this trait doesn’t function at the start of Angmar's next turn.

Multiattack. Angmar uses its Screech of Despair and makes five attacks. 

Sword. Melee Weapon Attack: +12 to hit, reach 5ft., one target. Hit: 10 (1d8 + 5) slashing damage. If Flame Blade is active, the attack deals 21 (6d6) fire damage instead. 

Flail. Melee Weapon Attack: +12 to hit, range 10ft, one target. Hit: 31 (4d12 + 5) bludgeoning damage. Each time Angmar misses with a Flail attack 1d12 damage is added to the next hit made with it until the end of his turn. 

Screech of Despair (Recharge 5-6). Angmar lets forth a horrible, mind-shattering screech. Each living creature within 120 feet of Angmar that can hear it must make a DC 20 Wisdom saving throw. On a failed save, a creature takes 45 (10d8) psychic damage and becomes frightened for 1 minute. If the saving throw fails by 5 or more, the creature rolls on the Short Term Madness Table. On a successful save, a creature takes half the psychic damage and doesn’t become frightened. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the frightening effect of the Angmar's Screech of Despair for the next 24 hours.

Flame Blade. Angmar sets his sword alight for 10 minutes. For the duration the sword deals an extra 6d6 damage with each hit. 
The flaming blade sheds bright light in a 10-foot radius and dim light for an additional 10 feet.