Aquarius is one of the two 'elementals' created by FireWater. Aquarius controls all cold in the universe of which it it in. Aquarius uses the power that FireWater has.
FireWater had regenerated after a fight with the Entity from over a trillion years ago. He wanted to get support from his work, as he will need more time to create Xenontryptophyl. To help do the work for him, he created Flarius and Aquarius. They would go to a selected universe and protect the heat and the cold.
Aquarius was weaker than Flarius, but has more time to use the powers they have over Flarius. If Aquarius was low on power, he would send water to Xenontryptophyl as his signal for FireWater to help him. This is also why Xenontryptophyl gained intense amounts of mass after it was completed in creation. Aquarius will use this signal before they are in danger, so that they have water after the amount of water they had used to warn FireWater. Aquarius will lose all power if not regenerated once every two billion years, minus the amount used as a signal.
Aquarius has never been in a intense battle with anyone. If you wanted to defeat Aquarius, you would need to pour seven hundred million tons of molten lava onto them. You will need to force the lava onto Aquarius, as they are nearly as cold as the freezing point of Nitrogen. They can also be massively weakened if you create a temperature any lower than -459.67 degrees Fahrenheit, the point at which atom can not move in. If you go lower, Aquarius will no longer continue distributing cold temperatures across the universe it is in. This then also means that any temperate below 0 degrees Fahrenheit will never be able to be obtained again. If someone were capable of making to temperate any lower than 0 degrees Fahrenheit again, the universe they are in will immediately encounter a heat death, destroying anything inside of the universe, including the universe.
Aquarius has split himself into undecillions of tiny pieces, most are barely visable. The Entity has attempted twice to stopping his work, but most of the many pieces of Aquarius are atomic. The Entity is barely able to destroy anything of that scale, and can not see any of them. Aquarius will signal FireWater to regenerate him again 734 million years from now. Flarius and Aquarius will continue to protect all heat in the universe until they will leave the universe they are in. They will leave the universe they are in directly before something happens to the universe that will destroy it entirely.