In order to ascend Cammuravi and Ethel, you’ll first need to unlock Cammuravi as a hero and level up his Seraph class to level 10 with Taion. Once this is done, progress in the story until you reach Colony Gamma Omega and enter the lab with Cammuravi in the party. Ethel will be with you and ask if she can use the pod to get stronger. Agreeing to help her will result in you regaining Ethel as a hero and both her and Cammuravi’s classes will unlock allowing you to level them both up to 20.