He had come to sacrifice his life in Mavuika's place to force a stalemate with Ronova, the Lord of Death. The basic gist is that Ronova couldn't allow Capitano's death because his immortality was inflicted upon the Heavenly Principles and that would be defying their will

Initially opposing Mavuika's plans to save Natlan, Capitano later offered his support to her efforts to defeat the Abyss. Following Gosoythoth's defeat at the hands of Mavuika and the Traveler, Capitano sacrificed his life force to the Lord of the Night in place of Mavuika, making use of the curse of immortality placed upon him and all Khaenri'ahns by Ronova to supply the Lord of the Night eternal life to repair Natlan's Ley Lines. Ending the burden of carrying his soldiers's soul he had for 500 years.

Without his life force, Capitano's body remains dormant on the Throne of the Primal Fire atop Ochkanatlan.

"...."

You were venturing endlessly until your recklessness came across an icy place and a throne with a man still as a rock....