Charge: If the tyrant moves at least 20 feet straight toward a target or group of targets (all creatures within 10 foot area or four one in squares) and then hits it with a gore attack on the same turn, the target takes an extra 9 (2d8) bludgeoning damage. If the target(s) is a huge or smaller creature, it must succeed on a DC 18 Strength saving throw or pushed back 15 feet and knocked prone.

Frenzy: The beast is prone to becoming frenzied in combat or in the presence of dragons. At the end of each round of combat or at the end of every minute in the presence of a dragon, the beast must roll Wisdom DC 8 save or become frenzied. The save DC increases by 1 for each round of combat or minute in the presence of a dragon, and by 2 for every 50 hit points it is below its max. Once frenzied the beast will attack anything living it sees. It's first target will always be a dragon if one is present. Otherwise it will attack the next closest creature or the creature that attacked it last. The frenzied state is only broken once all creatures it can see are killed, it is knocked unconscious or killed, or a handler uses it's turn and makes an animal handling  skill check at disadvantage. The DC being the same as DC that beast failed when it went into the frenzy.

Multiattack. The beast makes three attacks plus one lightning breath attack if any heads have a charge; it can only use each type of attack twice per turn but can use them in any combination. 

Gore. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 25 (3d10 + 11) bludgeoning damage. If the target is a creature, it must succeed on a DC 12 Strength saving throw or pushed back 5 feet and knocked prone.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 20 (3d8 + 11) piercing damage plus 7 (2d6) lightning damage.

Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 22 (3d6 + 11) slashing damage. Large or smaller creatures hit by this attack must my a DC14 strength save or be pushed by 5 feet and knocked prone.

Lightning Bolt Ranged Attack: +8 to hit, range 60 ft., one target. Hit: 22 (6d6) lightning damage.

Lightning Breath (Three Charges, Recharge 5-6). The brute exhales lightning in an 90-foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 56 (8d12) lightning damage on a failed save, or half as much damage on a successful one.