Constricting Grasp

Use this ability no more than twice per day,
after achieving full success on an attack roll
against a humanoid opponent. If you do, your
attack deals no damage, and you instead choke
the target's neck. Until they break free, they
are silenced (they cannot speak, use spells, or
take any spell-like actions) and cannot take any
action other than attacking you. This effect ends
when they successfully attack you. After some
number of rounds, the opponent may pass out.