CA (Custos Arcanorum, keeper of secrets) is a historical academic degree in magic. It was originated by the Arcane Helix, though at times other institutions have awarded it. CA being more part of the Equestrian academic system, no such institution has ever been located in Eastern Ponyland (including the Isle of Yore).

The focus of the CA is difficult to frame succinctly in 21st century human terms. It is a magical research degree, but focusing on the interpretation, assessment and synthesis of diverse sources of magical and technical lore rather than on physico-magical experimentation in the laboratory.