Crucible Knight

Aspect of the Crucible (Mythic Trait; Recharges after a Short or Long rest). If the Crucible Knight is reduced to 0 hit points, it doesn't die or fall unconscious. Instead, it regains 139 hit points. In addition, it gains a +1 to AC, as well as the "Phase 2" actions and movement. When this activates, all creatures (besides the Crucible Knight) within a 10 ft. radius must make a Dex save or take 10 (3d6) Radiant damage. It may also immediately move up to 60 feet with its Fly speed and make a Greatsword attack when it stops moving.

Bleed Level. The Crucible Knight cannot be bled.

Multiattack. The Crucible Knight can make four attacks on its turn: one Seismic Wave attack and three Greatsword attacks.

Multiattack (Phase 2). The Crucible Knight can make four attacks on its turn: three Greatsword attacks and one Tail Spin attack.

Ordovis's Greatsword. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 13 (2d8 + 4) Piercing + 8 (2d4 + 5) Radiant damage. 

Crucible Hornshield. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 6 (1d6 + 4) Bludgeoning + 13 (2d12) Piercing damage. The target must make a DC 17 Str save upon a hit or be pushed five feet back and be knocked prone.

Seismic Wave. Ranged Attack: DC 17, 15 ft. cone. All creatures in the cone must make a Dex save or take 19 (3d12) Bludgeoning damage.

Tail Spin (Phase 2). Melee Weapon Attack: +9 to hit, reach 45 ft., 1 target. Hit: 8 (1d8 + 4) Bludgeoning + 9 (2d8) Radiant damage. 

Holy Tail (Phase 2). The Crucible Knight can use a Tail Spin attack as a reaction to being hit by a melee attack.

If the Crucible Knight's mythic trait is active, it can use the options below as legendary actions. The Crucible Knight can take 2 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. The Crucible Knight regains spent legendary actions at the start of its turn.

Fly (Costs 1 Action). The Crucible Knight can fly up to 60 feet.

Tail Spin (Costs 1 Action). The Crucible Knight can make a Tail Spin attack.