Rune Slot

Like magic items, Focus and Power Runes need to be attuned before they can be used – although unlike magic items this requires the use of certain Abilities (Focus Rune Attunement, Power Rune Attunement or Rune Mastery). Focus Runes take up a single Rune Slot once attuned, Power Runes and Advanced Focus Runes take up two, and Advanced Power Runes use three. By default the number of Rune Slots you have is equal to your Concentration.