Well if Crota walked into the vault of glass he would be lost in time because that is Atheon's realm and he has complete control over time and space. If Atheon fought Crota in Crota's palace then Atheon could knock the shields down, but would wipe when Crota enraged because of the oversoul. At a neutral site I think Atheon would win because he still controls time and space. He could banish Crota to some forgot time/ place and then go cause havoc somewhere else. Crota only has power of wizard blasts, big sword, and no health regeneration in his immediate proximity. If Crota is banished then Atheon regens health. Overall Atheon wins.