You create a tiny bead of supercompressed matter in a chosen space within range, causing a 5-foot wide black hole to form in that space.  The black hole continues to grow in size and power throughout the spell's duration.

When the spell ends, either because your concentration is broken or because you decide to end it, the black hole collapses in on itself with low roar and winks out of existence with an explosion of cosmic energy that spreads around corners.  Each creature within the radius of the spell's gravity well, centered on the black hole, must make a Strength or Dexterity saving throw (target's choice).  On a failed save, a creature takes damage equal to the spell's total accumulated damage and is pushed in a straight line away from the center to the nearest unoccupied space outside of the sphere, where it falls prone, or half as much damage and half that distance without falling prone on a successful one.  The explosion caused by the black hole's collapse damages objects and structures in the area.

Any creature in a space the black hole occupies is automatically incapacitated for the remainder of the spell's duration and must make a Constitution saving throw during each turn they spend in the black hole's space. On a failed save, that creature takes damage equal to the spell's current total accumulated damage, or half as much damage on a successful one.

The black hole generates a gravity well in a sphere centered on itself which pulls anything inside it towards the black hole.  The area within the gravity well is considered difficult terrain.  Any ranged attack or area of effect that makes contact in any way with the gravity well is immediately drawn in, turning the black hole into its target.  If the black hole is not reduced to 0 hit points by the ranged attack, the ranged attack is consumed by the black hole.  Area spells using a spell slot of 6th level or higher will affect targets (including the black hole) in its intended area as normal before being consumed.  Any object that is dropped within the gravity well, including debris knocked loose from damaged structures, is also drawn towards the black hole and consumed contact.

The black hole is automatically targeted by any ranged attack or area of effect that originates from inside, or makes contact in any way with its gravity well.  If the original target was not the black hole, its target becomes the black hole.  The black hole has an AC of 15, automatically succeeds on all Strength and Constitution saving throws but automatically fails all other saving throws.  It initially has 100 hit points.  Any time the black hole grows, its remaining hit points double.  If the black hole is reduced to 0 hit points, the spell ends and it collapses.  It is immune to bludgeoning, piercing, and slashing damage from both non-magical and magical weapons and any weapon that makes contact with it is instantly destroyed and consumed.  It is immune to all conditions as well as to acid, necrotic, poison, psychic, and radiant damage  It has resistance against cold, fire, lightning, and thunder damage, but has vulnerability to force damage.

Any creature that starts or ends its turn within the radius of the gravity well must succeed on a Strength saving throw, or be pulled towards the black hole.

At the start of each of your turns, the gravity well deals half of the spell's accumulated damage to all structures inside it.  A structure that is destroyed inside the gravity well generates 1d8 pieces of debris, which are immediately pulled into the black hole.  A creature standing between a destroyed structure and the black hole must make a Dexterity save for each piece of debris that passes through their space, taking 1d4 bludgeoning damage and moving 5 feet closer to the black hole for each failed save.  Any section of a structure that comes into contact with the black hole is instantly destroyed and is considered to have generated a number of pieces of debris equal to the number of spaces the destroyed section occupied.

The spell's base black hole's base radius is 0 feet (occupying only 1 space), its base damage is 5d6 bludgeoning, cold, and force damage, its base gravity well is a 15-foot-radius sphere centered on the black hole's original space, the base distance a creature is pulled on a failed Strength saving throw within the gravity well is 10 feet, and the base DC for all saving throws for this spell equals your spell DC.

While the spell has not ended, it grows larger and more powerful each time one of the following conditions are met:

• your turn ends
• a creature is incapacitated by the black hole for the first time
• an item, piece of debris, ranged attack, or area effect is consumed by the black hole

Each time any of these conditions are met, the spell grows in all of the following ways:

• the black hole's radius increases by 5 feet
• the spell's damage doubles
• the radius of its gravity well increases by 15 feet
• the distance a creature is pulled on a failed Strength saving throw within the gravity well increases by 10 feet
• the DC for all saving throws for this spell increases by 1

The black hole can be defused by a antimagic field spell so long as its area of effect encompasses all spaces occupied by the black hole.  It can also be defused by being targeted by a dispel magic spell that is cast using a spell slot of 8th level or higher, or a disintegrate spell, likewise cast using a spell slot of 8th level or higher.  When black hole is defused by one of these spells, it ceases to exist without collapsing or causing the corresponding explosion.