Power (パワー Pawā) is a characteristic of SIGNI cards. A SIGNI's base power (基本パワー Kihon Pawā) is located on the bottom left of the card. Whenever two SIGNI battle due to an attack, if the attacking SIGNI's power is equal to or greater than the SIGNI it is battling, the attacked SIGNI is vanished; otherwise, both SIGNI stay on the field.
Certain effects can + (plus) (+(プラス)Purasu) and − (minus) (-(マイナス) Mainasu) the power of SIGNI, correspondingly increasing or decreasing its power. If a SIGNI's power drops to 0 or less, it is vanished as a rule-based action. Additionally, certain effects can modify a SIGNI's base power; these effects are not considered to "plus" or "minus" the SIGNI's power, even if it increases or decreases the SIGNI's power.
Many effects exist that vanish SIGNI depending on their power, including effects that vanish SIGNI below a certain power threshold, effects that vanish SIGNI above a certain power threshold, and effects that decrease a SIGNI's power. Generally, effects that vanish SIGNI with more power are more costly and difficult to use, making SIGNI with higher power harder to vanish and thus more durable.