in "Size manipulator" you spawn with a device that grants the user the ability to change size. just like antman from marvel. the device is designed to be used in a "minecraft but-" or "i beat minecraft with" challenge. also a player can just regularly play using the device. there is no crafting receipe- the player spawns into the world with the device, as well as they cannot remove it. if your in survival you CAN just elemante yourself, dropping the device and then saving it. however next time you spawn into the world, it will force you to have the device again. if you use this device in a video, please give a shout out.
(sales pitch) spawn into a new world with the Device PRE-installed on your character! at the cost of a chest plate you gain the power to scale your body, hearts and jump strength to your character size. become huge to tank lots of damage, or shrink to fit through gaps other mobs can't! use this unique mix of elements to your advantage and see if you can't beat the game. IN HARDCORE!