Little remains of the Royal Guard Captain besides the battered and beat up armor she barely keeps bound to her scarred limbs.The only fraction of her sanity left comes out when she visits Papyrus on the edge of Waterfall.
Undyne never had a head for puzzles, but the Hunger has made her an exceptionally patient predator; she will lie in wait to ambush any prey that wanders into her territory, sometimes for days. She is deceptively quick, but her armor makes such a ruckus that stalking is extremely inefficient. She’ll only give chase if she’s certain she can capture her prey.
Because she sports several rows of jagged teeth, she has a problem with drooling, and she cannot speak very well (not that she needs to, she just screams at everything anyways). Her skin is covered in a thin film of toxic mucus; anyone that touches her will be horribly poisoned, with the exception of monsters that don’t have skin.
Undyne is an apex predator, and a force to be reckoned with. However, for all her strengths, her one drawback is her desperate need to remain hydrated. Because of this, Undyne cannot venture far from Waterfall without threat of literally shriveling up.
Her ‘spear’ is just a really, really sharp mace at this point. She’s welded on so many razors, broken blades, and even stuck on bits of broken glass that it’s horribly balanced, but her Hunger-addled mind no longer grasps this fact, only capable of understanding its lethality. She keeps a strip of Alphys’s lab coat tied around its shaft, the only thing that was left of her girlfriend that she had managed to retrieve before the Amalgamates ran her out of the lab.
She remembers little of the past but the Hunger, Papyrus and Sans, and the scrap of her love’s coat. She regularly meets with Papyrus for playdates, romping and chasing each other and "training" in the first room of Waterfall, the closest she and he ever come to normalcy.