Spears, a green lock, and a full Undyne duel

Spoilers

Bridge, numbers, then what you can carry

Genocide players meet her as boss number three, the chase still inside Waterfall, Monster Kid blocking the bridge and turning to face the protagonist, Undyne stepping between them, a single strike emptying her HP, a lie about the wound, a warning for Monster Kid to run, and a refusal to turn to dust that her DETERMINATION, together with dreams and with what monsters and humans still hoped, forges into the Undying shape.

Her Japanese name is ふじみのアンダイン, and the wiki's figures are 23000 HP, attack 99 with a bracketed 12, defense 99 with a bracketed 5, and 1500 EXP. ACT offers Check and nothing else, the text calling her a heroine that her own DETERMINATION reformed so she could save Earth, with Serious Mode locked the entire battle. A swing that fails to drop her gets her own wording, not a summary: "You're gonna have to try a little harder than THAT." Spare is refused, and so is flee, even while the heart is still red.

The walk in uses But the Earth Refused to Die, the duel itself uses Battle Against a True Hero, and once she falls she trusts Alphys to have warned Asgore about absorbing the six human SOULs, with her last words that the world will live on.

Blows against her are multiplied by 21, and anything under 600 is rewritten into a 600–666 result, while her own spears connect for 8 to 14. Any level from 8 through 13 is legal: climbing adds HP and also strips one mercy frame per level, leaving you 17 to 21 frames instead of the usual 30. Frames can be bought back, at the cost of attack, from the Torn Notebook and the Cloudy Glasses, and the seller is Undertale's Gerson in his Waterfall shop, not the Chapter 4 hammer. Ballet Shoes shorten the duel, so fewer patterns appear, but dropping into the dump closes off those shoes and the Old Tutu. Sans is the other Genocide boss in this roster, Omega Flowey is the Neutral fight that follows Asgore, and roaringknightfight.com keeps a separate copy of tripoid's project.

Spoilers

Locked feet, then the rings that close

tripoid's build can be finished from a keyboard, arrows for the heart and the menus, Z to select, X to cancel, with WASD missing and no touch pad either, and the spear map below is the full Genocide Undying battle rather than a cutoff demo.

Feet stay planted while the colour is green, and the guard only covers the four sides of the box, never a diagonal. A blue spear goes red to mark the next hit, and that red spear is the one you owe a block. Yellow spears reverse before they arrive, so you cover the opposite side from where they first showed, which starts on the second green cycle. Fast spears and slow spears share the same wave. Later, one green wave hides the red mark: a single slow red spear sits among fast blue spears from every edge, and colour stops being information. Another wave circles in groups of four yellow, then four plain, then four yellow, the first two groups traveling counter-clockwise and the last group traveling clockwise.

• She keeps an internal Challenge number, green hits lower it, the arrows ease off, and those green waves also run longer.
• First red pattern after the opening greens: the box shrinks, three columns of spears rise, and a gap one pixel wide sits between the left column and the middle column. The original battle creeps into that gap by holding the back key, and tripoid mapped that slow step onto X. Without the slow step, park along the top and hop sideways only when a spear is about to rise into you.
• The other red wave in that stretch comes from every side on a wider board, so keep your feet moving, because spears cross the whole box and a corner is not cover.
• A pair of seven-spear rings closes on you, and only after that second ring does the locked colour return.
• After the final green waves the duel loops: rings of six converge while the space between rings shrinks, you travel in wide circles and slip the gaps, and a spear that has already met in the middle cannot hurt you.
• JCoxeye's no-hit notes call the spinning eight-spear rings her roughest pattern: stay nearly planted, take the gap when it opens, and expect the spin to relax as those spears come inward.
• Single spears come in fast and aimed, and a quicker three-column box returns as well.
• Length changes with what you wear: shoes at 7 attack wrap the duel up in roughly fifteen to eighteen patterns instead of a longer string, Waterfall's notebook costs 55G for 2 attack and 6 invincibility, the glasses cost 30G for 5 defense and 9 invincibility, and that Waterfall seller is Undertale's Gerson, which is why the extra frames can be worth the weaker swing; the shoes and the Old Tutu both become unreachable after the drop into the dump, and a level anywhere from 8 to 13 means more HP plus one fewer invincibility frame for each step up.