ANNIVERSARY P1 UT Soul OPs Boss Rush Extended is a fan game based on the popular game Undertale by Toby Fox. Developed by AverageGamerW, this game is a celebration of the first anniversary of the Soul OPs series.

In this fan game, players can expect a challenging boss rush experience. The game features an extended version of the boss rush mode from the original Soul OPs game, with additional content and new boss battles. It pays homage to various alternate universes (AUs) created by fans of Undertale. The game gives credit to all the creators of these AUs, making it a collaborative effort.

Fans of Undertale and the Soul OPs series will appreciate the attention to detail and the challenging gameplay offered in ANNIVERSARY P1 UT Soul OPs Boss Rush Extended. It is a free game available on the Roblox platform, allowing players to enjoy this fan-made experience without any cost.