Champion Arcturus

Unstable Magic.  Whenever he fails any saving throw all attack die for his spells change. Roll a d6 for type of die and a d20 for how many. Example: old fire ball 8d6 new fire ball 5d12

Swift Movement. Arcturus is unhindered by spells and terrain that affect his movement.

Spellcasting. Arcturus is a 20th-level spellcaster. His spellcasting ability is intelligence (spell save DC 21, +10 to hit with spell attacks). Arcturus has all spells prepared and the following spell slots available:
Cantrips (at will)
1st level (5 slots), 2nd level (3 slots), 3rd level (3 slots), 4th level (2 slots), 5th level (2 slots), 6th (2 slots), 7th (1 slot), 8th (1 slot), 9th (1 slot)

Multi-attack. Arcturus can make up to four actions in one turn.

Longsword. Melee Weapon Attack: +10 to hit, reach 5 ft., 2 targets. Hit: 24 (3d8 + 10) [Slashing] damage. 

Spellcasting. Arcturus uses any one spell. Any spell that requires 1 action or longer now take that number of his useable actions. example  1 turn now takes 1 action.

Legendary Action. Arcturus uses a Legendary action.

Uncanny Dodge. Can ignore up to 3 critical attack rolls.

Arcturus can take 4 legendary actions, choosing from the options below. Only one legendary action option can be used at a time. Arcturus regains spent legendary actions at the start of his turn. If all legendary actions are spent in one turn Arcturus must wait 3 turns before he regains any.

Divine Blade (Uses 2 legendary actions). Arcturus is provided with holy energy to his blade. He deals an extra 2d8 radiant and 1d8 fire damage. Does 1.5x damage to undead.

Replenish (Uses 3 legendary actions). All of Arcturus' used spell slots are restored.

Wrath of the Sun (uses 4 legendary actions). Arcturus creates an orb of light and sends it flying down to the ground to a location within 400ft of himself. The orb creates an explosion with a 200ft blast radius. All creatures within the 200ft blast radius must make a DC 21 Dexterity saving throw or take 7d20 radiant, fire, and force of each, undead take and extra 1.5 damage, Or half that on a successful one.