Embrace the Void

Ascend the Pantheon of Hallownest - the fifth and final Godhome boss rush, and the single hardest thing in the game. Over forty bosses back to back, culminating in new fights (Pure Vessel, the Nightmare King) and finally the Absolute Radiance. Beat the Absolute Radiance at the peak for the game's ultimate ending and this achievement. The very top of the mountain - expect it to take a very long time and many, many runs. (Optionally delivering a Delicate Flower to the Godseeker first changes the ending cutscene but grants the same achievement.)