Undyne the Undying

Martial Poise. Undyne can't be surprised, unless incapaciated and doesn't provoke opportunity attacks.

You're Green Now! If targeted creature is under the effects of flanking, deal an extra 2d10 force damage for every attack.

Commander. Every successful usage of Rend will degrade the target's AC by 2.

Undying. If Undyne reaches 0 hp, she'll return to half health and max hp halved until next long rest.

Multiattack. Undyne can make 4 Spear of Justice attacks. If at least one of these attacks hit, she may use Rend as a Bonus Action

Spear of Justice (Melee). Melee Weapon Attack: +13 to hit, reach 5 ft., 1 target. Hit: 19 (2d10 + 8) force damage. 

Spear of Justice (Ranged). Ranged Weapon Attack: +13 to hit, range 60/120 ft., 1 target. Hit: 16 (2d10 + 5) force damage.

The Heroine Appears. (Recharge 5-6) Undyne summons 10 spears to impale every hostile target within 120 ft of her. Targets must succeed on a DC 22 DEX save. She may then use Rend.

Rend. Undyne can target all creatures that has been hit with Spears of Justice this turn within 120 ft of her. Targets has to make a DC 22 Strength saving throw or 3d10 and 2d10 per extra spear that is on the target.

Undyne has 3 legendary actions.

Spear Throw (Costs 1 Actions). Throw a Spear of Justice.

Rally (Costs 2 Actions). Undyne yells at her allies to move up to half their speed.