You cast cards using Power in Eternal, and you gain Power by playing various Power cards. The five basic Power cards are Justice Sigil, Fire Sigil, Shadow Sigil, Time Sigil and Primal Sigil.

In addition to providing one Power, most Power cards provide one or more Influence. There are five types of Influence, corresponding to the five factions. Most cards have both a Power cost, shown in the top left corner, and an Influence requirement, shown as faction symbols to the right of the cost. However, unlike Power, Influence is not used up when a card is played. For example, if you only have one Time influence, you can still play multiple cards that require a Time Influence in one turn, as long as you have enough Power to play all of them.