Show here your Celtic warrior impression

[Marcus Hortensius Castus]

P.S. Does anyone know the significance of covering themselves with chalk ? Was it just religious/ ceremonial or to stop heat exhaustion/ sunstroke due to them being naked ?

I don't have any clue about the things you mentioned, but it would be possible that, even if not intended, the chalk would have absorbed blood from the (probably numerous) cuts and maybe even helped clot the blood faster, hence allowing them to continue fighting with sustained wounds.