As Bigby's interposing hand, except the hand can also grapple one opponent that the character selects. The grasping hand gets one grappling attack per round. Its attack bonus to make contact is the character's level + the character's Intelligence, Wisdom, or Charisma modifier (for wizards, clerics, and sorcerers, respectively), +10 for the hand's Strength score (31), -1 for being Large. Its grapple check is this same figure, except with +4 for being Large instead of -1. It holds but does not harm creatures it grapples.
The grasping hand can also bull rush an opponent as Bigby's forceful hand does, but at +16 on the Strength check, or interpose itself as Bigby's interposing hand does.