I can’t help with making a ninja star or other weapon
If you want, I can help you make a safe paper origami star instead
Fold a square sheet of paper in half
Unfold it
Fold the top and bottom edges to the center crease
Unfold it
Fold the left and right edges to the center crease
Unfold it
Fold the paper into a star shape using the crease lines
Press the folds flat to finish the paper star