Undyne the Undying

Legendary Resistance (4/Day). If Undyne fails a saving throw, she can choose to succeed instead.

Magic Resistance. Undyne has advantage on saving throws against spells and magical effects. Undyne is also immune to all spells that would change her form or turn her undead.

Magical Equipment. Undyne’s attacks are considered magical.

Unreasonable. Deception and Persuasion checks made against Undyne are made with disadvantage. Deception and Persuasion checks made by evil-aligned creatures fail automatically.

Heroic Last Stand. Undyne has expertise in Wisdom and Chasima saving throws. When she succeeds a Wisdom or Charisma saving throw, she can use her reaction to make a Spear of Justice attack against the source.

Monsterkind’s Hero. Undyne is immune to being frightened, charmed, paralyzed, grappled and petrified. Intimidation checks against Undyne fail automatically. If Undyne is slain, all Monstrosities within 5 miles will immediately become hostile to Undyne’s killer.

Slayer of Evil. Undyne has advantage on all attacks made against evil-aligned creatures and their allies. When she rolls a 17 or higher on a hit roll against an evil-aligned creature, she crits. If she slays an evil-aligned creature, she gains another turn (doesn’t stack; once per turn).

Undying Determination. When Undyne is reduced to zero hit points, she rolls a d20. On a 5 or below, she dies. If she rolls above a 5, she recovers xd10 hit points (x = dice number rolled). On a 20, she recovers half her hit points. Undyne also recovers 5d10 (27) hit points at the start of her turn.

Innate Spellcasting. Undynes innate spellcasting ability is Charisma (spell save DC 19, +11 to hit with spell attacks). Undyne can innately cast spells, requiring no material components:

At will: Aid, Compelled Duel, Heroism, Magic Weapon, Prayer of Healing, Spiritual Weapon, Wrathful Smite

3/Day: Crusader's Mantle, Locate Creature,  Protection from Energy, Spirit Shroud, Staggering Smite

1/Day: Dispel Evil and Good, Holy Weapon, Steel Wind Strike

Multiattack. Undyne makes three Spear of Justice attacks. She can follow any of them up by casting an at-will spell or with her Spear Ring or Refusal to Die action if available.

Spear of Justice. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 14 (2d6+7) piercing damage.

Spear Hail (1/day). An area made up of sheets of conjured spears appears in a location within 120ft of Undyne. The area consists of up to ten 10-foot cubes, which she can arrange as she wishes. Each cube must have at least one face adjacent to the face of another cube. Each creature in the area must make a DC 21 Dexterity saving throw. It takes 14d12 force damage on a failed save, or half as much damage on a successful one.

Refusal to Die (Recharge 6). Undyne channels her Determination to protect, healing her wounds. Undyne recovers 16d8 hit points and ends all negative effects on her.

Spear Ring (Recharge 6). Undyne chooses a spot within 60 ft. that she can see. In a 10 ft. radius centered on the spot, blue spears come out of the ground. Any creature within the area has to make a DC 18 Dexterity saving throw, taking 5d10 force damage or half as much on a successful one. Any creature within the area also cannot use their movement speed until the start of Undyne's next turn.

Heroic Counter (1/round). When Undyne is hit by a weapon attack, she can make an attack using her Spear of Justice action.

Undyne can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at one time and only at the end of another creature’s turn. Undyne regains spent legendary actions at the start of her turn.

Weapon Attack (1 Action). Undyne makes an attack using her Spear of Justice.

Spellcasting (1 Action). Undyne uses one of her at-will spells.

Power Jump (2 Actions). Undyne jumps up high into the air and lands on an unoccupied space within 60 ft. that she can see. When she lands, all creatures within 30 ft. of where she landed have to make a DC 18 Dexterity saving throw. On a fail, the targets take 18 (4d8) force damage and are knocked prone. The targets take half as much on a successful save.

Hope of Monsterkind (3 Actions). Undyne takes a deep breath and channels the hope all of monsterkind has in her, causing her to regain strength. Undyne recovers 72 (16d8) hit points and any 3/day spells. Additionally, she is resistant agains the next three attacks made against her.