Multiattack. Grugnur makes two longsword attacks.
Longsword +2. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit:23 (3d8 + 10) slashing damage, or 26 (3d10 + 10) slashing damage if used with both hands.
Rock. Ranged Weapon Attack: +12 to hit, range 60/240 ft., one target. Hit:30 (4d10 + 8) bludgeoning damage.