The Revolver's pulley wheel reduces friction on ropes moving through the carabiner. Placed where the pitch changes direction, it reduces rope drag and makes upward movement easier.
The Revolver can be used in an improvised hauling system to help your second over a crux, haul kit bags, or rescue your partner from a crevasse. Where normal carabiners in these systems cause energy to be lost as friction, the Revolver's pulley wheel makes hauling easier by converting more of your energy into movement.
A Revolver on your rack lets you reduce rope drag and make efficient mechanical advantage systems without the need for additional devices.