Bladesinger Master

Bladesong. 5 times per long rest, the Bladesinger Master can use a bonus action to start a Bladesong, which lasts for 1 minute and grants them the following benefits:

The Bladesinger Master gains a +4 bonus to their AC, they can add +4 to the damage of their melee weapon attacks, their walking speed increases by 10 ft., they have advantage on Acrobatics checks, and they gain a +4 bonus to any CON saving throw they make to maintain their concentration on a spell.

It ends early if they are incapacitated, if they don medium or heavy armor or a shield, or use two hands to make an attack with a weapon. You can also dismiss the Bladesong at any time you choose (no action required).

Spellcasting. The [monster name] is a 14th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). The Bladesinger Master has following Wizard spells prepared:
Cantrips (at will): Booming Blade, Lightning Lure, Prestidigitation

1st level (4 slots): Mage Armor, Shield

2nd level (3 slots): Blur, Misty Step

3rd level (3 slots): Blink, Counterspell, Haste, Slow

4th level (3 slots): Banishment, Locate Creature

5th level (2 slots): Hold Monster, Steel Wind Strike

6th level (1 slots): True Seeing

7th level (1 slots): Prismatic Spray

Multiattack. The Bladesinger Master makes three attacks with their rapier.

Rapier. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 20 (3d8 + 5) piercing damage.

Rapier (Bladesong Active). Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 24 (3d8 + 9) piercing damage.

Bladesong. The Blademaster Singer activates their Bladesong.

Song of Defense. When the Bladesinger Master takes damage while their Bladesong is active, they can use their reaction to expend one spell slot and reduce that damage by an amount equal to five times the spell slot’s level.