Barrel Dragon

Multiattack. The tyrannosaurus makes two attacks: one with its bite and one with its tail. It can't make both attacks against the same target.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 33 (4d12 + 7) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the tyrannosaurus can't bite another target.

Tail. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage.

The barrel dragon can take 1 legendary action can be used at one time and only at the end of another creature’s turn. The barrel dragon regains spent legendary actions at the start of its turn.

Cannon Blast. The barrel dragons claws grip tight to the ground, it lowers its head forward aligning its head, back and tail straight as a blade. Several parts of its mechanical armor open up and you can see behind them are vents containing fan blades that begin spinning and suck in the air around it. It opens it maw wide with a roar. A large cylindrical barrel extends from the recess of this creatures mouth. A ball of electrical energy can be scene forming in its mouth. It exhales a destructive electrical energy.

When the  barrel dragon uses its cannon blast, forming a line 100 feet long and 5 feet wide out from the barrel dragon. Each creature in the line must make a DC 16 dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.

The lightning ignites flammable objects in the area that aren’t being worn or carried.