The Spellcaster is able to manipulate the shadows surrounding the enemy target and Grapple the opponents shadow with the other shadows, the target appears to stop and start physically choking as though being strangled. The target will take 2d8 + (wis Modifier) in psychic damage every round until either the target creature escapes or the 1 minute has passed

on a successful wisdom save the target avoids or escapes the grapple at which point concentration is lost for the spell caster.
As a monk on the Path of The Souls Shadow, this costs you 1 Ki point as an action, or 2 Ki points as a bonus action.