Asteroth was a cosmic being of pure evil that sought to destroy all life in the universe and became an opponent of the Marvel superhero Beta-Ray Bill.
Long ago she was banished to the Cosmic Hell by her own species to safeguard the universe but was freed many centuries later when Stardust opened a portal to this dimension during a battle with Beta-Ray Bill.
Weakened from her centuries of imprisonment Asteroth went on a rampage, consuming as much as she could in order to grow ever more powerful from the devastation.
she is based on the Lovecraftian entity known as Azathoth and just like that entity was apparently limitless in power, at her "base" level she was able to effortlessly consume planets and she rapidly grew in power - capable of devouring entire star systems, then galaxies and it was theorized has she not been defeated she would of been able to devour the universe itself.
She claimed to have been born from the chaos caused by the creation of the universe and embodied the universe's tears and sorrow - this would explain her malevolent nature and why she had been imprisoned for untold centuries before the start of the story in which she was accidentally awoken.