Aspect of Vecna

Special Equipment. The aspect is attuned to the Book of Vile Darkness, he is immune to all of the book's negative effects (including detrimental properties), and treats it as his spellbook, using his spell save DC for any of the book's effects that require a saving throw. He also carries a magic +3 dagger named Afterthought. In the hands of anyone other than Vecna or his aspect, it is a +2 dagger.

Aura of the Damned. After the aspect rolls initiative, an aura of flying spectral entities fills a 30-foot radius centered on him, and moves with him. All creatures that aren't undead within the aura immediately take 18 (4d8) necrotic damage. The creature also takes this damage whenever it enters the aura for the first time on a turn or starts its turn there. The first time each round a creature that isn't undead takes at least 10 necrotic damage at a time while within range (including from this trait), it must succeed on a DC 25 Wisdom saving throw or be frightened of the aspect until the end of its next turn. The aspect can deactivate and reactivate this aura as a bonus action.

Turn Immunity. The aspect is immune to effects that turn undead.

Undying. If the Aspect of Vecna is slain, his soul refuses to accept its fate and lives on as a disembodied spirit that fashions a new body for itself after 1d100 years. The aspect's new body appears within 100 miles of where he was slain. When the new body is complete, the aspect regains all his hit points and becomes active again.

Unusual Nature. The aspect doesn't require air, food, drink, or sleep.

Vecna's Weakness. The aspect is vulnerable to all damage dealt to him by the Sword of Kas or by anyone who has grafted one of Vecna's body parts.

Multiattack. The aspect first uses Chrono Spurt (if available), then uses either Rotten Fate, or casts a spell with a casting time of 1 action using Spellcasting. He then finally makes two attacks with Afterthought.

Afterthought. Melee Weapon Attack: +16 to hit, reach 5 ft., one target. Hit: 9 (1d4+7) piercing damage plus 18 (4d8) necrotic damage. If the target is a creature other than undead, it becomes afflicted with entropic magic. At the end of each of its turns, the target must succeed on a DC 22 Constitution saving throw or take 18 (4d8) necrotic damage, reducing its maximum hit points by the necrotic damage dealt. If the aspect has been reduced to below half its maximum hit points during the combat encounter, it also gains temporary hit points equal to half the necrotic damage dealt on a failed save. Any temporary hit points gained in this way are cumulative, up to a maximum number of 90 temporary hit points. On a successful save, the target only takes half damage and none of its other effects. This effect ends when the target succeeds on this save three times; they don't have to be consecutive. Unless it succeeds on this save, the afflicted target can't regain hit points.

Chrono Spurt (Recharge 5–6). The aspect gains an additional reaction per round, but only once per turn.

Rotten Fate. The aspect causes necrotic magic to engulf one creature he can see within 120 feet of himself. The target must succeed on a DC 24 Constitution saving throw or take 96 (8d8+60) necrotic damage on a failed save or half as much damage on a successful one. A creature other than an undead that is killed by this magic rises at the start of the aspect's next turn and acts immediately after him in the initiative order. The creature retains its statistics and is under the aspect's and Vecna's control, but it is an undead creature and only has half of its original maximum hit points.

Spellcasting. The aspect casts one of the following spells, requiring no material components and using Intelligence as the spellcasting ability (spell save DC 25):

At will: animate dead (as an action), detect magic, dispel magic, fly, lightning bolt, mage hand, prestidigitation

2/day each: dimension door, invisibility, scrying (as an action)

1/day each: dominate monster, foresight (as an action), globe of invulnerability, mirage arcane (as an action), plane shift (self only), prismatic wall

Vile Teleport. The aspect teleports, along with any equipment he is wearing or carrying, up to 30 feet to an unoccupied space he can see. He can cause each creature of his choice within 15 feet of his destination space to take 10 (3d6) psychic damage. If at least one creature takes this damage, the aspect regains 50 (20d4) hit points.

Divine Backlash (5/Day). The aspect's limited divine power, while potent, can backfire when used. If the aspect fails a saving throw, he can choose to succeed instead. When he does so, he can't regain hit points, he loses all temporary hit points, all damage dealt by effects originating from him is halved (including from lair actions), and creatures have advantage on all saving throws against any effects originating from him and against his spells until the end of his next turn.

Dread Counterspell. The aspect utters a dread word to interrupt a creature he can see that is casting a spell. If the spell is 4th level or lower, it fails and has no effect. If the spell is 5th level or higher, the aspect makes an Intelligence check (DC 10 + the spell's level). On a success, the spell fails and has no effect. Whatever the spell's level, the caster takes 10 (3d6) psychic damage if the spell fails.

Fell Rebuke. In response to being hit by an attack, the aspect utters a fell word, dealing 21 (6d6) necrotic damage to the attacker, and the aspect teleports, along with any equipment he is wearing or carrying, up to 30 feet to an unoccupied space he can see.

Will of Vile Darkness. If the aspect casts a spell that requires concentration but is already concentrating on another spell, he instead has the Book of Vile Darkness concentrate on the spell instead. He can only have the book concentrate on one spell in this way at any time. If the aspect ever needs to make a Constitution saving throw to maintain concentration while concentrating on two spells in this way, he only makes one saving throw to maintain concentration on both spells.

The Aspect of Vecna can take 3 legendary actions, choosing from the options below. Only one legendary option can be used at a time and only at the end of another creature's turn. The aspect regains spent legendary actions at the start of its turn.

Attack. The aspect makes an attack with Afterthought.

Chrono Spurt (Costs 2 Actions). The aspect attempts to recharge and then use Chrono Spurt (if recharged).

Disrupt Life (Costs 3 Actions). Each living creature within the aspect's Aura of the Damned (if active) must make a DC 25 Constitution saving throw against this magic, taking 70 (20d6) necrotic damage on a failed save, or half as much damage on a success. This damage ignores resistance and creatures immune to this damage always take half the result.