Undyne

Legendary Resistance (3/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.

Special Equipment. Undyne carries a magic spear named Spear of Justice. In any other hands, the Spear of Justice is a +3 spear.

Heroic Mentality. Undyne has expertise in Wisdom and Charisma saving throws. She also has advantage on saving throws made against being grappled or restrained.

Heat Sensitivity. Undyne is vulnerable to fire damage. If she is in an area with high temperatures, she falls unconscious if she stays there for more than 5 minutes.

Bane of Evil. Undyne has advantage on weapon attacks made against evil-aligned creatures. If she slays an evil-aligned creature, she regains 10d8 hit points.

Overwhelming Determination. When Undyne is reduced to zero hit points, she can choose to resist death temporarily. As she begins to die and melt, she can immediately take another turn, gaining another use of her multiattack action. She also gains resistance to all damage types while she is melting. After the round is over, she fully melts and dies. If Undyne was slain by an evil-aligned creature, she instead transforms into Undyne the Undying.

Multiattack. Undyne can make two spear attacks (melee or ranged) during her turn. She can replace one of them with her Ring of Spears or Spear Trap action.

Spear of Justice (Melee). Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 13 (2d6 + 6) piercing damage.

Spear of Justice (Ranged). Ranged Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 13 (2d6 + 6) piercing damage.

Multijab. Undyne rapidly jabs her spear at a target within 20 ft. Undyne makes five regular weapon attacks against the target. For each successful hit, the target takes 13 (2d6 + 6) force damage.

Ring of Spears. Undyne summons a ring of spears around one or more creatures, up to three. The target has to make a DC 17 Dexterity saving throw. On a fail, the target takes 22 (5d8) force damage or half as much on a successful save.

Spear Trap. Undyne picks up to five spots within 90 ft. she can see, where light blue spears shoot out of the ground. A target within 10 ft. of the spots has to make a DC 17 Dexterity saving throw, taking 16 (3d10) force damage on a failed save or half as much on a successful one.

Soul Change - Green (Recharge 6). Undyne charges her spear with strange green energy and slashes at a target within 20 ft. of her. The target has to make a DC 20 Wisdom saving throw. On a fail, the target has their movement speed reduced to 0 ft. and cannot be moved by any means, but has their AC increased by 2. This effect lasts until Undyne dispells it, Undyne uses it on a different creature or combat against Undyne ends.