Armored Titan

Armored Bulk. Due to the weight of the Titan's armour, the Armored Titan has disadvantage on Dexterity checks and saving throws.

Curse of Ymir. The Titan Shifter possessing this Titan will die 13 years after gaining the Armored Titan.

Regeneration. As long as the Titan has 1 hit point, it regains 20 hit points at the start of its turn. The Titan Shifter within the Titan's body doesn't benefit from this trait, but regrows any lost body parts while inside the Titan.

Siege Monster. The Armored Titan deals double damage against objects and structures.

Titan Steam. A Titan gives off a large amount of heat, and it produces steam around its wounds as it regenerates. The area around any open wounds the Titan has are lightly obscured by this steam, and upon death, the Titan's corpse is moderately obscured until the entire corpse evaporates.

Transformation. A Titan Shifter can use their action to transform into a Titan, in this case, the Armored Titan. The Titan keeps the Titan Shifter's Intelligence, Wisdom, and Charisma scores (the above scores are placeholders), as well as the Shifter's alignment. When the Titan dies, or when the Shifter takes an action to end the transformation, the Shifter is ejected from the Titan's body, which instantly drops to 0 hit points and begins evaporating, unless the Shifter rejoins their Titan body within the next minute.

Weak Point. The Titan's weak point is its nape. A creature can target the nape, which has an AC of 23 and 30 hit points. If the attack against the nape misses, it misses the Titan altogether. The nape does not benefit from the Titan's regeneration trait, and the Titan dies if the nape is destroyed. Any damage done to the nape is done to the Titan Shifter within the Titan's body. If the Titan Shifter dies, the Titan dies.

Multiattack. The Attack Titan can make three attacks.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 21 (4d6 + 7) piercing damage, and the target must make a DC 18 Dexterity saving throw or be grappled by the Titan (escape DC 18). The Titan can only grapple one creature in this way, and cannot make Bite attacks while grappling a creature. 

Slam. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 25 (4d8 + 7) bludgeoning damage.

Charge (Recharge 5-6). The Armored Titan moves up to its speed in a straight line. Each creature in its way must make a DC 19 Dexterity saving throw, taking 55 (10d10) bludgeoning damage and being carried with the Armored Titan until the end of its movement. The creature takes half the damage and is not carried with the Armored Titan on a successful save. This damage is done to any structures in the Armored Titan's way as well.