Masks ("máscaras") have been used dating back to the beginnings of lucha libre in the early part of the 20th century, and have a historical significance to Mexico in general, dating to the days of the Aztecs. Early masks were very simple with basic colors to distinguish the wrestler. In modern lucha libre, masks are colorfully designed to evoke the images of animals, gods, ancient heroes and other archetypes, whose identity the "luchador" takes on during a performance. Virtually all wrestlers in Mexico will start their careers wearing masks, but over the span of their careers, a large number of them will be unmasked. Sometimes, a wrestler slated for retirement will be unmasked in his final bout or at the beginning of a final tour, signifying loss of identity as that character. Sometimes, losing the mask signifies the end of a gimmick with the wrestler moving on to a new gimmick and mask. The mask is considered sacred to a degree, so much so that fully removing an opponent's mask during a match is grounds for disqualification.