I think the use of the 'helmet' (of all things) to kill Conrad is because it symbolises 'Alphonso the good'. It is his helmet IIRC, just grown larger and changed it's material of construction.
The peasant, had observed it to be so.
So I think it means that 'Good' is going to destroy the 'bad'.
I don't know if there was a sword with the statue, because it would have been more normal for a sword to come flying to slay him.
Unless this large sword forms a 'set' with the 'helmet' so was not there in the first place.