Crush the Giant Snapping Turtle

Amphibious Mount. Crush can breathe air and water. Anyone riding Crush can breathe air and water.

Stable. Whenever an effect knocks Crush prone, he can make a DC 10 Constitution saving throw to avoid being knocked prone. A prone turtle is upside down. To stand up, Crush must succeed on a DC 10 Dexterity check on his turn and then use all his movement for that turn.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 22 (4d8 + 4) slashing damage.

Thunderous Charge. Melee Weapon Attack: +8 to hit, Crush travels in a straight line for 20 feet that do not cost his movement before colliding with one target. On Hit:  33 (6d8 + 6) bludgeoning damage. Crush and his target are both prone and Crush is affected by his Stable trait.

Hurl Foe. Melee and Ranged Weapon Attack +6 to hit, reach 5 ft and 60ft, two targets, one adjacent and one at a range of 60ft or less. Hit: 18 (4d6 + 4) bludgeoning damage as Crush bites down on a armored part of the creature within 5ft of him and hurls them up to 60ft away at a second, they take the same damage as they collide. You may choose to throw the first target at any area where there is no enemy within 60ft, in which case they will take no damage, and simply be at the targeted location.

Taunting Shell. Crush makes a big noise, stomping and squeaking, drawing the enemies attention before retreating inside his shell. His AC increases by 6 and any enemy within 20ft of him must succeed on a DC 17 Wisdom saving throw or be compelled to attack him and ignore any other allies of Crush until Crush emerges from his shell as a bonus action or uses the Emergent Strike bonus action on a following turn. While within his shell, Crush's attack range for all attacks is reduced to 0ft and he cannot move or take any action other than emerging from his shell. When he exits his shell all attributes return to normal levels.

Emergent Strike. If Crush is inside his shell, he can take advantage of his Snapping Turtle reaction when he exits his shell and his melee range increases to 5ft. This does not occur if he simply emerges without taking this action. 

Snapping Turtle. Crush makes one Bite attack against an enemy that either exits or enter his range, he cannot do this more than once per turn.

Defending Shell. Crush takes the attack damage if an attack would hit Yuna or another ally he likes and he is within 5ft of her. He wants to protect his friends.

Of course he is legendary, but he doesn't have any legendary actions