Rogue Chosen (Mythic Trait; Recharges after a Short/Long Rest). The first time Manshoon is reduced to 0 hit points, he regains 125 of his hit points. his Spell Corruptions and Spell Slots gain 1 in their categories, and he creates an aura of corrupted magic. When a creature receives magical healing from a spell within 15 feet of Manshoon, the creature that healed it must make an Intelligence saving throw against Manshoon's spell save DC. On a failed save, the healing magic affects Manshoon as well, and he can reroll the dice with an advantage to himself even if the spell only targets one or a specific number of creatures. 

Always Prepared. Manshoon has cast teleport as a contingency, which comes into effect when he faces a hostile foe. Additionally, if possible, he casts fire shield, mind blank, see invisibility, stoneskin on himself prior to combat.

Dual-Focused. Manshoon is capable of maintaining concentration on two spells at the same time. Any time a concentration check is required, Manshoon must make one check for each spell. 

Manshoon's Legendary Resistance. (3/Day). If Manshoon fails a saving throw, he can choose to succeed instead. Additionally, when using this feature, Manshoon may target any one creature within 30 feet of him and make it the target of the spell he chose to resist.

Magic Resistance. Manshoon has an advantage on saving throws against spells and other magical effects.

Attire of The Original:  As Amos, he wears a unique robe of the archmagi that gives him an advantage on saving throws against spells and other magical effects while also having the abilities of a cloak of many fashions. Manshoon wields a walking cane with the stats of a staff of power. Roll 3d10 to determine how many charges the staff has remaining, and deal slashing damage rather than bludgeoning in melee. The handle resembles the Zhentarim winged snake, with the wings outstretched and the tail descending down the shaft of the cane. 

Manshoon's Archive. A tome that weighs 20 pounds and has properties of an enduring spellbook, it radiates a collection of amassed magic. The spellbook can be pulled and stored out of the very Weave, and can be recalled to Manshoon within 60 feet. It contains all the spells Manshoon has prepared plus the following spells: alter self, animate dead, antimagic field, arcane lock, dominate monster, dream, etherealness, Evard's black tentacles, feather fall, gaseous form, geas, gentle repose, glyph of warding, hold monster, major image, mass suggestion, phantom steed, protection from evil and good, symbol, teleportation circle, Tenser's floating disk, tongues, true seeing, vampiric touch, wall of fire, and wish. 

Spell Corruptions (4/Day). Whenever Manshoon casts a spell, he can corrupt it using one of the following spell corruptions. He can only use one spell corruption when casting a spell.

• Distorted Dilation. When a spell Manshoon casts a spell with a duration of 1 minute or longer ends, he can extend its duration to last at most 1 hour. 
• Duplicitous Casting. When Manshoon casts a spell that targets only one creature, he can target 1d4 additional creatures of his choice within range of the spell.
• False Magic. If a spell misses a target creature, reroll and pick a different target than the original. Manshoon changes his attack to be toward the new target, so long as they are within walking range of the original target.
• Twisted Elements. When Manshoon casts a spell that deals a type of damage from the following list, he can instead change its type to another of the listed types; acid, cold, fire, lightning, poison, or thunder. If a creature makes a saving throw to resist the damage, it rolls with a disadvantage on the first saving throw made against it.
• Unnatural Extensions. Manshoon can increase the range of a spell that is 5 feet or greater to double the range of the spell. If casting a spell that has a range of touch, the range of the spell is 30 feet. 
• Unchallenged Ambition. The spell and its effects can create no sound, smell, taste, or are visible. The spell otherwise affects creatures normally and requires any verbal components as usual.

Spellcasting. Manshoon is an 20th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 23, +16 to hit with spell attacks). Manshoon can cast disguise self and invisibility at will and has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, shocking grasp

1st level (4 slots):  alarm, detect magic, identify, mage armor*, magic missile, shield

2nd level (3 slots): detect thoughts, invisibility, mirror image, see invisibility*

3rd level (3 slots): counterspell, dispel magic, fly, fireball, lightning bolt, sending, slow

4th level (3 slots): banishment, blight, confusion, dimension door, fire shield, greater invisibility, polymorph, stoneskin*

5th level (3 slots): Bigby's hand, cone of cold, cloudkill, scrying, telekinesis, wall of force

6th level (2 slot):  contingency*, disintegrate, flesh to stone, globe of invulnerability

7th level (2 slot): finger of death, simulacrum, teleport*

8th level (2 slot): [spell)dominate monster[/spell], feeblemind, mind blank*

9th level (2 slot): imprisonment, power word kill, prismatic wall, time stop

*The archmage casts these spells on itself before combat.

Zhentarim's Master. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 9 (1d6 + 6) slashing damage, or 10 (1d8 + 6) slashing damage when used with two hands. Manshoon can expend 1 of the staff’s charges to deal an extra 7 (1d8) force damage on a hit.

Magical Palm. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 6 (1d8) bludgeoning damage.

Misty Step Manshoon dissipates into the Weave using misty step, and moves up to his full movement speed without provoking opportunity attacks. Any equipment he is wearing or carrying moves with him.

Manshoon the Manyfaced can take up to 3 reactions each round, but only 1 per turn.

Counterspell. Manshoon interrupts a creature in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, he makes an intelligence check (DC 10+ the spell’s level). On a success, the creature's spell fails and has no effect.

Shield. Manshoon summons a barrier of magical force to protect him. Until the end of the turn, his AC is increased by +5, including against the attack that triggered it, and he takes no damage from magic missile.

Manshoon 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. Amos regains spent legendary actions at the start of his turn.

Cantrip (Costs 1 Action). Manshoon casts a cantrip.

Spell Cast (Costs 1-3 Actions). Manshoon can cast a 1st-, 2nd-, or 3rd-level spell he has prepared, expending a spell slot if appropriate. Doing so costs 1 legendary action per level of the spell.

If Manshoon's mythic trait is active, he gains 3 mythic actions to use toward the options below. He can only use the options below as mythic actions, and only once per round as long as he has hit points remaining from Rogue Chosen. 

Spell Fury (Costs 1-3 Actions). Manshoon can cast a 4th, 5th, or 6th-level spell he has prepared, expending a spell slot if appropriate. Doing so costs 1 mythic action per level of the spell.

Syphon Counterspell. Manshoon interrupts the casting of a spell with a counterspell, dissipating it with a wave of his hand. If the spell is 3rd level or lower, it fails and has no effect. If the spell is 4th level or higher, he makes an intelligence check (DC 10+ the spell’s level). On a success, he causes the spell to fail but then funnels it into himself. The caster loses an addional spell slot of the casted spell's level.

Power Overwhelming. When Manshoon casts a spell of 1st through 6th level that deals damage, he can inflict maximum damage with the spell. When Manshoon casts a wizard spell of 6th through 9th level that deals damage, he can reroll a number of the damage dice up to his Intelligence modifier (minimum of one.) He must use the new rolls.