Caligarde's Claw

 You ward an area up to a 50’ cube within range with an invisible, Medium-sized claw made of force that hovers within and lasts for the duration. The claw is an object that has AC 20 and hit points equal to your hit point maximum. It acts on your turn and has an action and a reaction. If it drops to 0 hit points, the spell ends. A hit from Mordenkainen's Sword instantly destroys it. When cast, you can designate any number of allied creatures that will not trigger an attack from the claw.

When first created, the claw acts as a sentry: it will use its reaction to attack the first intruder to enter the warded area. On its turn, it will use its action to continue attacking the same intruder if it remains within the warded area. If the creature dies or leaves the warded area, the claw will instead use its action to attack another intruder in the warded area that's closest to the center, or ready itself for a new intruder if there are none to attack. Because it is invisible, the claw attacks with advantage against creatures unable to see it. On a hit, the target takes force damage equal to 2d10 plus your spellcasting ability modifier. The claw appears briefly after the attack, then fades from view within seconds. The claw can attack a total of ten times, after which the spell ends.

If you are within range, you can use your bonus action to designate which creature the claw should attack on its turn. It will continue to do so as long as it is able. You can also modify the list of allied creatures that will not be attacked at this time.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the claw’s damage increases by 1d10 for every two slot levels beyond 4th.

Adapted from the AD&D 2nd edition book Pages From The Mages.