Musician

In reality: None, was always condition to take up arms. Every depictions that shows no helmet is either stylized for fashion or the helmet is well hidden beneath a hat. https://en.wikipedia.org/wiki/Secrete_%28helmet%29 This goes only for that period though. In antiquitity and the dark age you could get away with being bare-headed. Fun-fact: (Selbst im 18.Jhd trugen Kürassiere in Wahrheit Gitter/casquets über ihren Dreispitzen, um die zu verstärken, weil die sonst alle durch Kopfschläge gestorben wären. https://upload.wikimedia.org/wikipedia/commons/a/aa/Cuirassier_hat_and_casquet.png?20200901204113 ) In fantasy: Plenty.