Prayer accompanied most rites, and probably consisted of traditional formulæ, on the exact recital of which depended their value. The Druids invoked a god during the mistletoe rite, and at a Galatian sacrifice, offered to bring birds to destroy grasshoppers, prayer was made to the birds themselves.[850] In Mona, at the Roman invasion, the Druids raised their arms and uttered prayers for deliverance, at the same time cursing the invaders, and Boudicca invoked the protection of the goddess Andrasta in a similar manner.[851] Chants were sung by the "priestesses" of Sena to raise storms, and they were also sung by warriors both before and after a battle, to the accompaniment of a measured dance and the clashing of arms.[852] These warrior chants were composed by bards, and probably included invocations of the war-gods and the recital of famous deeds. They may also have been of the nature of spells ensuring the help of the gods, like the war-cries uttered by a whole army to the sound of trumpets.[853] These consisted of the name of a god, of a tribe or clan, or of some well-known phrase. As the recital of a divine name is often supposed to force the god to help, these cries had thus a magical aspect, while they also struck terror into the foe.[854] Warriors also advanced dancing to the fray, and they are depicted on coins dancing on horseback or before a sword, which was worshipped by the Celts.[855] The Celtiberian festival at the full moon consisted entirely of dancing. The dance is a primitive method of expressing religious emotion, and where it imitates certain actions, it is intended by magical influence to crown the actions themselves with success. It is thus a kind of acted prayer with magical results. DIVINATION.