These are two very warm hats that can be used simply to keep warm, or for fun

The King’s Helm is based on historic examples of helmets with built in crowns - I suspect these were more for show and tournament use than for actual battle, but they certainly are fun. Ornamented with optional jewels in each point, they are quite showy. You could also knit the helmet without the crown.

The Viking Helmet is more in the realm of fantasy - there is no evidence that actual Viking helmets had horns - it seems to be more an operatic convention. You can, of course, make this helmet without the horns.

Either helmet can be made with a chin strap or with an aventail (chain mail neck armour). Add the beard to either helmet, also. The beard can be made removable by using snap fasteners to attach it. I do NOT recommend hook and loop tape for this purpose.

Each helmet requires two skeins of the base yarn (grey). The crown, the beard, and the horns require one skein each of an appropriate colour.