Here's an easy way to create a showstopping costume.
Horns (and helmet): Use the basic horn instructions to make two long, curved horns, leaving them unpainted. Tape them to a headband. Cut the bill from a baseball cap, and cover the entire cap with duct tape. Attach the headband to the top of the cap with more duct tape. Decorate with electrical tape.
Shield and sword: Paint a large cardboard circle and trim it with duct tape. For a handle, tape a cardboard loop to the back of the shield. For the sword, use two layers of cardboard covered in duct tape and electrical tape.
Tunic: Cut a neck hole in a long rectangle of fake fur. Add a rope belt.