What are the Aegislash's Speed IV's? If it has low Speed IV's, then you could go for a mainly Special Tank set, like,
an Aegislash holding an Iron Ball, EV's could be 252 SpA, 252 SpD, and 4 Atk, and the moveset could be King's Shield/Toxic/Gyro Ball/Shadow Ball. It has 26 SpD IV's, which is pretty good, and, if you get Bottle Caps, you can max out the physical attack IV.