Signet

Signets are special skills that don't require energy. The most popular signet is Resurrection Signet

As said signets don't need energy to activate, but their downside is that they have a long activation and recharge times.

Signets may also be usefull when you have hexes (like Backfire and Guilt) that prevent you from using spells. Beware there are signet prevention hexes too, but they are more rarely used.