Source: Lords of Madness
A beholder with this feat can narrow its antimagic cone down to an eye ray that disjoins magic.
Prerequisite: Cha 19, Focused Antimagic, beholder with functional antimagic ability.
Benefit: As a standard action, the creature can reduce the cone-shaped area of effect of its central eye's antimagic cone down to a razor-thin eye ray. If the creature hits a magical effect or magic item with this narrowed eye ray, it disjoins the effect or item as if it had cast Mordenkainen's disjunction on the effect or item.
Beholders avoid using this narrowed ray on magic items since the destruction of a magic item also destroys a potential source of magic that could be used to charge their dweomerlobes.