Adui
Just go capture dark expanse worlds. Its not like you are destroying them, just connecting them. There is no need to risk yourself. If that grandmaster notices you it will be problematic and also citizens of that world will get your fate buff which is something celestials are proficient with it. So, they migh(will) notice the change and made a search at that planet to find the fate power that empowers that world's life forms. Just go to dark expanse capture some vampire worlds or find small worlds with no life and directly conquer them. There is 0 risk. The important thing is the amount of mana, which can be achieved by quantitity ove quality strategy. Find bunch od small worlds.