Simply put, the Shadow Monk gains the ability to cast the Darkness spell, but I'm struggling to see a use for it except as concealment during an escape.
Way of the Shadow monk receives Darkness (among a few other spells) and is able to cast it as a Ki ability using 2 Ki points. The effect of the spell reads:
Magical darkness spreads from a point you choose within range to fill a 15-foot-radius sphere for the duration. The darkness spreads around corners. A creature with darkvision can’t see through this darkness, and nonmagical light can’t illuminate it.
If the point you choose is on an object you are holding or one that isn’t being worn or carried, the darkness emanates from the object and moves with it. Completely covering the source of the darkness with an opaque object, such as a bowl or a helm, blocks the darkness.
If any of this spell’s area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled.
Now this is useful because at level 6 the Shadow Monk gains the ability to teleport from any spot in darkness (or heavily obscured) to any other space in darkness, but I'm trying to see how this could actually be useful beyond setting up a teleport (since I would be blinded in the darkness).
Preferably I'd like a way to attack without being blinded by the darkness to make use of all the good monk features and even possibly cast it on my weapon to be a roving cloud of Darkness and punches.