Components: V, S, M (an eggshell and a dragonhide glove with claws--if a dragon, one's own claw works as well)
Duration: Concentration, up to 10 minutes
Lists: Wizard, Cleric (almost exclusively followers of Tiamat)
As Bigby's Hand (see also the errata here), but with the following changes:
The "hand" that appears is a Huge, shimmering dragon claw. Its base AC is 24, DEX 14 (+2), STR 30 (+10).
Instead of Clenched Fist, you may use a Scratching Claw effect. Make a melee spell attack using your statistics, reach 5' from the hand; on hit, deal 4d10 slashing damage. The damage is considered magical for the sake of overcoming immunity or resistance.
The Forceful Hand effect (here Forceful Claw) has advantage on any Large or smaller creature. You can move it 5' + 5' * [your spellcasting modifier]; if you had advantage on the STR check, you can double this distance. If the creature is Small or smaller, you can redouble this distance.
The Grasping Hand effect (here Grasping Claw) can grapple a Gargantuan or smaller creature, and has advantage on creatures that are Huge or smaller. While grappling a creature, this effect can be used to crush it for a base damage of 6d6 bludgeoning damage.
Interposing Hand is called Interposing Claw, but has no mechanical changes.
At higher levels: Add 2d10 to the damage caused by the Scratching Claw effect, and 2d6 to the Grasping Claw effect, for each spell slot level above the 7th. At 9th level, double again the distance for the Forceful Claw effect.
Yes, this spell is used. No, I'm not telling you where--at least, not yet.