Type: General
Source: Dragon #351
Through concentration and preparation your mind can hold special magical energy.
Prerequisite: Ability to cast 1st-level arcane spells.
Benefit: As long as you have at least one arcane spell slot available (either a prepared arcane spell or the ability to cast an arcane spell spontaneously), you may make a DC 20 Concentration check to gain arcane focus. This use of Concentration requires a full-round action that provokes an attack of opportunity. Once you acquire arcane focus, you remain focused until you expend it, become unconscious, fall asleep, or cast all available arcane spells.
When you have arcane focus, you may expend your focus as a swift action on any single Concentration check you make thereafter. If you expend your focus for this purpose, treat your Concentration check as if you rolled a 15 (similar to taking 10). You may expend your arcane focus in this way even if you could not normally take 10 on a skill check, such as during combat. You may instead expend your arcane focus to activate an arcane feat you possess and gain one of the benefits of that feat.
Special: A wizard may select Arcane Focus as a wizard bonus feat.