Undyne

Brave. Undyne has advantage on saving throws against being frightened.

Overwhelming Determination. If Undyne is reduced to 0 hit points, she does not fall unconscious, and dies at the end of her next turn. When she dies, her body and equipment she was wearing or carrying disintegrate. If Undyne takes damage exceeding her hit point maximum from an evil creature, she instead transforms into Undyne the Undying.

Multiattack. Undyne uses her Hero Soul if she can then makes two melee attacks or two ranged attacks.

Eldritch Spear. Melee Spell Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) force damage.

Eldritch Spear. Ranged Spell Attack: +4 to hit, range 60 ft., one target. Hit: 5 (1d6 + 2) force damage. 

Hero Soul (Recharge 4-6). Undyne forces a creature that she can see within 60 feet to fight her head on. The creature must succeed on a DC 13 Wisdom saving throw, or for 1 minute, it has disadvantage on attack rolls against other creatures except Undyne, and must make a DC 13 Wisdom saving throw every time it attempts to move to a space that is more than 60 feet away from Undyne; if it succeeds on this saving throw, this ability doesn't restrict the target's movement for that turn.

The ability ends if Undyne attacks any other creature, if a creature friendly to Undyne damages the target or casts a harmful spell at it, or if Undyne ends her turn more than 60 feet away from the target.