Ambidextrous

Ambidextrous reduces the cost of using grenades and scrolls by 1 AP when your offhand is free.

Ambidextrous is a talent.

Overview

Ambidextrous reduces the AP cost of grenades and scrolls by 1 when the character's off-hand slot is empty.

Ambidextrous is a niche talent that benefits characters who rely heavily on grenades or scrolls. In practice, most builds do not use enough consumables to justify spending a talent point on this over offensive options such as  Executioner or  Elemental Affinity.
The talent is incompatible with Dual Wielding and shield-wielding builds, as both occupy the off-hand slot.
Unequipping an off-hand item does not cost AP. A character can keep something equipped in the off-hand for its stat bonuses and simply unequip it before using a grenade or scroll.
Scrolls can provide access to powerful spells outside a character's primary skill school. Ambidextrous reduces their AP cost, but scrolls are finite and expensive, limiting the talent's long-term value.