The Helix Blade Demo is most likely a demonstration version of a Nintendo 64 game featuring a weapon or element called "Helix Blade." It's highly probable that it's an unreleased prototype, homebrew creation, or a promotional build of a larger game. Gameplay would likely showcase a segment of the intended full game, focusing on combat or mechanics involving the Helix Blade.  Pinpointing the developer(s) and project details requires additional information.

The Helix Blade Demo

The Dark World