Colchis Bull

Celestial Bronze Body. This creature is a construct made entirely of Celestial Bronze giving it immunity to edged weapons and most forms of magic, including any that would change it's form.

Legendary Resistance (3/Day). If the Colchis Bull fails a saving throw, it can choose to succeed instead.

Trampling Charge. If the Colchis Bull moves at least 15 feet straight toward a creature and then hits it with a gore attack on the same turn, that target must succeed on a DC 20 Strength saving throw or be knocked prone. If the target is prone, the Colchis Bull can make one stomp attack against it as a bonus action.

Innate Spellcasting. The Colchis Bull's spellcasting ability is Constitution (spell save DC 20). It can innately cast the following spells, requiring no material components:
3/day each: Fireball, Delayed Blast Fireball

Multiattack. The Colchis Bull can use its Frightful Presence. It then makes 3 attacks: one with its gore, and two with its kick.

Stomp. Melee Weapon Attack: +12 to hit, reach 10 ft., one prone target. Hit: 22 (3d8 + 8) bludgeoning damage. 

Kick. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 18 (3d6 + 8) bludgeoning damage. 

Gore. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 20 (2d10 + 8) piercing damage.

Frightful Presence. Each creature of the Colchis Bull’s choice that is within 120 feet of the Colchis Bull and aware of it must succeed on a DC 18 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 effect ends for it, the creature is immune to the Colchis Bull’s Frightful Presence for the next 24 hours.

Fire Breath (Recharges 5-6). The Colchis Bull exhales fire in a 60-foot cone. Each creature in the area must make a DC 20 Dexterity saving throw, taking 70 (19d6) fire damage on a failed save, or half as much on a successful one.

The Colchis Bull can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Colchis Bull regains spent legendary actions at the start of its turn.

Kick Attack. The Colchis Bull makes a kick attack.

Gore Attack. The Colchis Bull makes a gore attack.

Double Stomp (Costs 2 Actions). The Colchis Bull makes 2 stomp attacks against a prone target

Upon reaching 50% Hit Points the Colchis Bull automatically enters its Overdrive mode, granting it powerful capabilities.

Overdrive (Below 50% Hit Points). The Colchis Bull activates its Overdrive Mode granting it +30 movement, stun resistance, and refreshing all spent spells and legendary resistances, as well as a re-roll of initiative with advantage taking the higher roll, Double Stomp's legendary action cost is halved. Any current effects such as stun, bindings or other immobilization effects are removed upon activating this ability. The Colchis Bull gains access to Concussive Blows and Battlelord while it is in Overdrive Mode.

Concussive Blows (Passive). All of the Colchis Bull's melee attacks require the target to succeed a DC 20 Strength throw or become stunned, the target must then make a DC 20 Constitution saving throw at the end of each of its turns with a successful save ending the effect. If the target is already stunned this knocks them prone.

Battlelord (Recharges 5-6). Upon Activation for 18 seconds if any creature makes a hostile action against the Colchis Bull it can take immediate action with it gaining a full turn worth of actions, Legendary actions are refreshed upon activation of this ability.