Big Terry

Amphibious. The dragon can breathe air and water.

Legendary Resistance (4/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Magic Resistance. Big Terry has advantage on saving throws against spells and other magical effects.

Spiked Explosion. Immediately after Big Terry uses an action or legendary action, it causes the spikes on its body to explode outward. Each creature within 40 feet of Big Terry must make a DC 24 Dexterity saving throw, taking 10(3d6) piercing damage and begin to bleed from a vicious wound on a failed save or half as much damage and do not bleed on a successful one. 

Vicious Wound. A creature suffering from a vicious wound loses 4(1d8) hit points at the start of each of its turns. Each time the creature suffers from another vicious wound, the damage dealt by the wound increases by 4(1d8). Any creature can take an action to stanch the would with a successful DC 18 Wisdom(Medicine) check. The would also closes if the target receives magical healing. 

Spiked Regrowth. Big Terry has spikes covering its body. When used, Broken, or Removed in any way the spikes regrow instantly. 

Multiattack. Big Terry can use its frightful presence. It the makes one Bite attack, one Horn attack, and two Claw attacks.

Bite. Melee Attack Roll: +16, reach 5 ft. Hit: 25 (4d8 + 7) Piercing damage.

Claw. Melee Attack Roll: +16, reach 10 ft. Hit: 14 (2d6 + 7) Slashing damage.

Horn. Melee Attack Roll: +16, reach 10 ft. Hit: 29 (4d10 + 7) Bludgeoning damage.

Wing. Melee Attack Roll: +16, reach 10 ft. Hit: 29 (4d10 + 7) Piercing damage.

Frightful Presence. Each creature of Big Terry's choice that is within 120 feet of Big Terry and ware of it must succeed on a DC 20 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effects ends for it, the creature is immune to Big Terry's Frightful Presence for the next 24 hours. 

Meteor Crash (Recharge 5–6). Big Terry leaps into the air using its wings to hover briefly before it comes crashing down in a 20 foot square area within 90 feet of its start. Each creature in the area must make a DC 24 Dexterity saving throw. Failure: 80 (23d6) Bludgeoning damage. Success: Half damage.

Dragon Eater. Big Terry feeds on the corpse of a dragon. A larger or smaller dragon is consumed whole, While Big Terry can feed on a huge or bigger dragon for up to 30 seconds. Each round Big Terry feeds on a dragon, it regains a number of hit points equal to that dragon's Challenge Rating. 

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn , Big Terry can expend a use to take one of the following actions. Big Terry regains all expended uses at the start of each its turns.

Hunger. Big Terry uses its dragon eater, but only heals for half the amount it normally would.

Wing Attack. Big Terry makes a wing attack.

Trample (Costs 2 Actions). Big Terry moves up to its speed. During this move it can move through the spaces of other creatures without provoking opportunity attacks. Each creature Big Terry moves through must make a Dexterity Saving Throw: DC 24,  Failure: 32 (4d10+7) Bludgeoning damage, and the target is knocked prone.