With this cloak, the breakable checkpoints will show a yellow crystal inside. Breaking one of these checkpoints will cause this crystal to appear, and picking up this crystal will activate the effect, making Specter Knight's will decrease to the default 4 points, as well as making Specter Knight's darkness slowly regenerate. While the effect is active, fireballs will be shot at close range with every swing of Specter Knight's scythe, and breaking more checkpoints will have no effect.
This effect will wear off if Specter Knight is defeated. In this case, the last unbroken checkpoint will show the same yellow crystal.
During New Game Plus, picking up the crystal will reduce the "Darkness + Will" to a maximum of 80 points (4 bars), but it will no longer run out through time (and still regenerates) until the effect wears off.