Arcane Knight

Brave. The Arcane Knight has advantage on saving throws against being frightened.

Magic Resistance. The Arcane Knight has advantage on saving throws against spells and other magical effects.

Mages Bane. If the Arcane Knight hits a target with a melee attack it can disrupt any ongoing spell or spell-like effect as if it was casting dispel magic at 5th level. 

Legendary Resistance (3/Day). If the Arcane Knight fails a saving throw, it can choose to succeed instead.  

Action Surge(1/day).
the Arcane Knight can push itself beyond its normal limits for a moment. On its turn, the Arcane Knight can take one additional action on top of its regular action. 

Second Wind (1/day). the Arcane Knight can use a bonus action to regain 20 hit points. 

Defense. the Arcane Knight has 2 additional AC when its wearing armor.

Sentinel. Whenever Arcane Knight hits a creature with an opportunity attack, its speed drops to 0 for the rest of the turn. This stops any movement they may have been taking. Creatures within Arcane Knights reach provoke opportunity attacks even if they took the Disengage action.

Spellcasting. The Arcane Knight is a 19th-level spell caster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). It has the following wizard spells prepared:

Cantrips (at will): Fire Bolt, Frostbite, Prestidigitation

1st level (4 slots): Shield, Absorb Elements, Magic missile

2nd level (3 slots): Scorching Ray,  Hold Person

3rd level (3 slots): Counterspell, Psionic Blast

4th level (1 slot): Resilient Sphere  

Multiattack. The Arcane Knight makes three melee attacks, or two melee attacks and casts one spell.

Glave. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 9 (1d10 + 4) slashing damage.

Parry. The Arcane Knight adds 5 to its AC against one melee attack that would hit it. To do so, the Arcane Knight must see the attacker and be wielding a melee weapon.

Cut Down the Caster. The Arcane Knight can make an attack of opportunity if a creature starts to cast a spell with reach, on a melee hit the arcane knight disrupts the spell and prevents the casting.    

Sentinel. When a creature within the Arcane Knights reach makes an attack against a target other than the Arcane Knight, it can use its reaction to make a melee weapon attack against the attacking creature.

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

Move. The Arcane Knight moves up to its speed without provoking opportunity attacks.

Weapon Attack. The Arcane Knight makes one weapon attack.

Cast one cantrip. The Arcane Knight casts one cantrip.   

Destroy one spell. (Costs 2 Actions). The Arcane Knight unravels one ongoing spell of 5th level or lower.