Of all the companions of our joyous ascent, there were only the two of us left.

Ascent : a climb or walk to the summit of a mountain or hill.
Decent : conforming with generally accepted standards of respectable or moral behaviour.
Descent : an act of moving downwards, dropping, or falling.
Descant : an independent treble melody sung or played above a basic melody.
Descendant : a person, plant, or animal that is descended from a particular ancestor.

Antonym of Ascent is Descent