Multiattack
The longbeard makes two attacks with its Augmented Atgeir. It cannot make two augmented attacks in the same turn.
Atgeir
Melee Weapon attack: +6 to hit, reach 10 ft., one target. Hit:  1d10+4  slashing damage.
Disarming Strike
Melee Weapon attack: +6 to hit, reach 10 ft., one target. Hit:  1d4+4  slashing damage and the target must succeed a DC 15 STR Save or its weapon is thrown 10 ft. away.
Eruption augmentation (1/Short Rest, +Bonus Action)
Melee Weapon attack: +6 to hit, reach 10 ft., one target. Hit: 1d10+4  slashing damage and at the end of your turn, lifting the weapon creates a pool of lave underneath the creature. Each creature within 5 ft. of the pool of your choice must succeed a DC 15 STR Save or take  4d6  fire damage.
Gravitas augmentation (1/Short Rest, +Bonus Action)
The Longbeard thrusts his weapon into the ground creating a gravity well. Each creature within 30 ft. of you that is Large or smaller is pulled upto 10 ft. towards you. Pulled creatures must succeed a DC 15 CON Save or take  1d6  force damage and be pulled another 10 ft. towards you.
Roar of the Earth augmentation (1/Short Rest, +Bonus Action
The Longbeard lets out a battle cry creating a powerful shockwave. Each creature within 10 ft. of you that is Large or smaller must succeed a DC 15 STR Save or be knocked prone.