It had no idea how it came to be, or if it had a past life somewhere. It just followed it's instinct and lived according to the flow of the world.
Wherever it felt the life energy that was responsible for its growth it chased after it and made sure to devour it, regardless of whatever stood in its path.
It continued this cycle for a long time, until someday it gained a sense of identity. It now knew about itself and now made plans to keep itself safe and alive.
Then it found a goal. It wasn't just looking for life energy based on instinct anymore. It watched itself grow everytime he devoured the life essence of others.
It was a creature born from the null, where chaos reigned and darkness and despair was the norm, but it found itself in a world of light and order. The only way it could grow was to devour the life energy of others and convert it into its origin.
It's goal was to devour as much energy as he could and reach the highest state possible. It was going to return home.