The masks are carved wood or moulded papier mache, often larger than a human head, and they are consecrated objects rather than costume. They show the wrathful protector deities of the tantric pantheon, the stag headed and bull headed forms, the citipati or skeleton lords who guard the charnel ground, and figures of the lineage teachers. Monks who wear them are understood to take on the deity's function for the duration of the dance, which is why the training is a religious discipline: the point is not that the audience should believe a deity is present, but that the dancer should perform the visualisation correctly while moving.
What the dance does, in its own terms, is clear an obstruction. A common structure has the dancers describe a slow circle to cymbals, drums and the long dungchen horns, subduing the forces hostile to the teaching, after which an effigy standing for those forces is destroyed at the close of the sequence. The pace is deliberate and heavy, closer to a procession than to anything quick, and the great festivals at which it is performed fall around the turn of the year in most traditions, at Losar or at the tsechu observances held in Bhutan and elsewhere. Lay people attend for merit and for the year ahead, and the occasion is a fair as well as a rite. Individual monasteries differ in sequence, mask and detail, and none of them regards the others as wrong.