What does a number in a circle represent?

In Riftbound, a number in a circle (e.g., [1], [2], [3]) represents an Energy cost.

These symbols indicate the amount of Energy required to play a card or activate an ability. You can find this information in the "Reference" section of the provided game documentation:

• [1]/[2]/[3]/...: Represents the energy cost of a card or ability.

If you are seeing these numbers in the text of a card, they are shorthand for the cost you must pay to play that card or use its effect.