You create a point pure void which swallows a 20-foot radius sphere of space, plunging it into magical darkness and forming a life devouring freezing void. A creature with darkvision can't see through this darkness, and nonmagical light can't illuminate it unless it comes from a spell of higher level than this one. A creature that starts their turn within the void must make a Constitution saving throw. On failure, they take 2d6 cold damage and 2d6 necrotic damage, and their speed is reduced by 5 feet. The reduction to their speed lasts until they start not inside the area of the void, and can stack with itself, up to a maximum effect of reducing a creature's speed to 5 feet. On a success, they take half as much damage and their speed is not reduced.