Actions

Multiattack The gryphon makes two attacks: one with its Beak and one with its Claws.

Beak Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 1d8+4 piercing damage.
Claws Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 2d6+4 slashing damage.

Reactions

I Want That! When this gryphon is hit with a melee weapon attack they can make a contested Strength check against the creature that attacked it to disarm them of their currently held item and hold it in their beak.
While this gryphon is holding a stolen weapon in its beak it cannot use its regular beak attack. Instead it must make an Improvised Weapon Attack: +6 1d20+6 to hit, reach 5 ft., one target. Hit: 1d4+4 blugeoning damage.
At the start of each of their turns the owner of this gryphon can make a contested Charisma Check against the gryphon to make it drop the stolen weapon.