Hypixel Metamorphosis

Hello! I'm making a mod on Mcreator and I found myself stuck in my programming of an object for a long time. But, a colleague told me about Hypixel and some features that could help me. Indeed, I am trying to make an object that allows the player to possess the entity that is hit by the projectile launched by the object. The function of Hypixel that my colleague told me about was metamorphosis. In fact, it is just a creature that follows the player. So my question is. How to reproduce this in code in Mcreator. I thank you in advance for your answers.