Undyne the Undying Fight

Undyne the Undying Fight is an intense bullet-hell boss encounter where you face the determined captain of the Royal Guard at her most powerful. After being mortally wounded defending Monster Kid, Undyne's incredible determination transforms her into Undyne the Undying - a far more powerful version hellbent on stopping your genocidal rampage. This epic fight takes place on a bridge in Waterfall, where Undyne unleashes increasingly complex spear patterns that come from all sides of the battle arena. The core mechanics revolve around navigating these bullet patterns while managing your SOUL's color state - Red mode allows free movement but makes you vulnerable, while Green mode roots you in place but lets you block incoming spears. Undyne can instantly switch your SOUL mode with a flick of her spear, forcing you to constantly adapt your strategy. What makes this fight particularly challenging is Undyne's persistence - she continues attacking even when her HP reaches zero, and the battle only ends when her determination finally fades. The fight demands perfect timing, spatial awareness, and quick reactions as the spear patterns become faster and more complex with each phase. This is considered one of the most difficult boss encounters in the game, testing your skills to their absolute limit against an opponent who literally refuses to die.