Imago
The imago(image) was a 3-D metal representation of the emperor who was currently in power or who had formed the army. It could also be a sign of the zodiac when the unit/legion was formed. It was carried by the imagnifier, one of the signiferi(sign-bearers), a position that was created in the army during the rule of Augustus(formerly Octavian) when the imperial cult* was first established. Because of this, the imago had political importance in addition of military importance. The imago was designed to help the soldiers feel strong in battle.
*imperial cult: a cult which identified rulers and some of their family with the authority over the sentate