You start with 6 Signa cards in hand, and use them to pay for special maneuvers - or to activate unactivated unit after Tempus Fugit is played. Notably, the cards you play don't naturally return to your hand - they go into the activation deck. So you are effectively surrendering control of this resource if you play it real early. Drawing 4 Signa cards in a row also causes shenanigans.
