You dont get a seperate AS in the box, you get special bits to make him stand out, ok u should have about 6 different helms for the AC: 1 with long ribbed horns with metal tips, one with curved horns the meet in the middle with mouth grill and 2 skulls in between the curved horns, 1 with doubleribbed horns that join with a skull on top with a Khorne symbol hanging from the skull. 1 bold headed with bionics with a horn growing out of it, 1 with 3 eyes pieces and a single ribbed horn and another with 4 horns and and eye symbol in the middle of the head.
You also should have a powerpack with skulls on top of the vents with horns growing out of them and 2 more horns on the power pack, you should also have a chest with a vent in the centre and chainmail.
You also should have 5 Icons which should be Khorne, Nurgle, Tzeentch, Slaanesh and undivided as well and a Icon staff.
If you dont have them id suggest taking it back or calling customer services explain the situation and they should be able to sort it.