Colossal Titan

Transformation. A Titan shifter can transform into a Titan, in this case, the Colossal Titan. When the Titan shifter in human (or humanoid) form has a purpose in his heart and damages themself, he or she shifts into a Titan. The Titan forms out of air and manifests in seconds. The shifters Intelligence, Wisdom, and Charisma scores stay the same (the ones in the stat block are placeholders). Once the Titan shifter wants to revert back to humanoid form, he or she will pop out of the Titan's nape, and the body will slowly melt into steam. Transforming into the Colossal Titan takes a huge amount of energy. After a transformation, the shifter must wait 3d10 days before transforming again. Once the transformation is available, the Colossal Titan will have 1/2 it's maximum HP on its transformation. For every additional day the transformation feature isn't used, the amount of HP the titan has when it transforms is increased by 50 (this cannot go above it's maximum HP). When the Colossal Titan transforms without full HP, the physical state of the titan reflects it.

Explosion When the titan shifter transforms into the Colossal Titan a huge explosion occurs. Every creature in a 250 feet sphere must make DC 25 Dexterity saving throw or take 130 (20d10) fire damage and 110 (20d10) force damage or half on a save. Any creature within 100 ft of the titan lose the saving throw no matter what, while every creature being more than 200 feet away from the titan only take half of the damage on a fail and take no damage on a success.

Legendary Resistance (5/day). If the Colossal Titan fails a saving throw, it can choose to succeed instead.

Siege Monster. The Colossal Titan deals double damage to objects and structures.

Weak Point. The nape of the Colossal Titan's neck is a weak point. An attack which specifically targets the Colossal Titan's nape deals damage to the person inside. If the person inside dies, the Titan will die. You must climb up the Colossal Titan to the nape with a Melee attack, or you can try to shoot it with a ranged weapon at disadvantage.

Kick. Melee Weapon Attack: +19 to hit, reach 80 ft., hits up to 5 creatures within a 10 ft. of cube. Hit: 154 (24d8 + 10) Bludgeoning damage. Target gets knocked back 2d4 x 10 feet and gets hit up in the air 1d6 x 10 feet. The target takes the appropriate fall damage and gets knocked Prone.

Punch. Melee Weapon Attack: +19 to hit, reach 50 ft., hits up to 3 creatures within a 5 ft. cube. Hit: 120 (20d10 + 10) Bludgeoning damage, and targets are knocked back 30 ft. and knocked prone.

Steam. The Colossal Titan releases steam from its body, forcing all targets within a 150 ft. sphere to make a DC 23 Dexterity saving throw, or take 110 (20d10) fire damage, or half on save. All creatures that failed the saving throw are blown back 1d4 x 50 feet. Being underwater doesn't grant resistance to this damage. When this attack is used, the Colossal Titan loses 50 Hit Points, as the steam comes from the skin of the titan evaporating. The Colossal Titan cannot use this feature if it is under 400 Hit Points.