Cart Titan

Transformation. A Titan shifter can transform into a Titan, in this case, the Cart Titan. When the Titan shifter in human (or humanoid) form has a purpose in his heart and damages himself, he or she shifts into a Titan. The Titan forms out of air and manifests in seconds. The shifter's Intelligence, Wisdom, and Charisma scores stay the same (the ones in the stat block are from the Pieck, the shifter from Attack on Titan). 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.

High Endurance The Cart Titan is exceptionally mobile and has high endurance, capable of long distance travel with ease. It gives the Cart Titan advantage on constitution saving throws when saving from exhaustion.

Regeneration. The Cart Titan recovers 20 hit points at the start of each of its turns, and 10 to the person inside the Titan. If the Cart Titan takes any form of damage to the nape of its neck, this trait doesn't function at the start of the Cart Titan's next turn. The Cart Titan only dies if it starts its turn with 0 hit points and doesn't regenerate.

Weak Point. The nape of the Cart Titan's neck is a weak point. An attack which specifically targets the Cart Titan's nape deals damage to the person inside (has 30 hp in the nape). If the person inside dies, the Cart Titan is destroyed. You must climb up the Cart Titan to the nape with a Melee attack, or you can try to shoot it with a ranged weapon at disadvantage.

Punch. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 20 (4d6 + 7) bludgeoning damage.

Bite Melee Weapon Attack +12 to hit, reach 10ft., one target. Hit 41 (8d8 + 9) Piercing damage, and If the target is large or smaller it is restrained.