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 131 hit points and gains a fly speed of 40 ft. for 1 hour.

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

Magic Resistance. The crucible knight has advantage on saving throws against spells and other magical effects.

Multiattack. The crucible knight makes three attacks, one with its staggering stomp and two with its greatsword.

Greatsword. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 25 (3d12 +7) slashing damage.

Shield Bash. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 7) bludgeoning damage.

Staggering Stomp. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 11 (4d6 + 5) piercing damage. The target must make a DC 18 Constitution saving throw, being stunned on a failed save. The target can repeat the saving throw at the start of its next turn. On a successful save, that creature is no longer stunned.

Shield Counter. When an enemy within 5 ft. of the crucible knight misses a melee weapon attack made against the crucible knight, the crucible knight can use its reaction or spend a legendary action to make a shield bash attack against that enemy.

The crucible 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 ulcerated tree spirit regains spent legendary actions at the start of its turn.

Slash. The crucible knight makes one attack with its greatsword.

Seismic Wave. (Costs 2 Actions). The crucible knight makes one attack with its staggering stomp.

If the crucible knight's mythic trait is active, it can use the options below as legendary actions for 1 hour after using Aspect of the Crucible.

Crucible Flight. (Costs 2 Actions). The crucible knight flies up to 30 ft. in a straight line without provoking opportunity attacks, making a greatsword attack against each enemy creature in that line.

Crucible Tail. (Costs 2 Actions). The crucible knight summons a magical tail that swipes around the crucible knight in a 30 ft. circle. Each creature in that area must make a DC 18 Dexterity saving throw, taking 24 (4d12) bludgeoning damage and being knocked prone on a failed save.