Even though, we only see him as a commentary in the Dragon Ball Super’s Tournament of Power, the Grand Priest is undoubtedly the strongest character in the anime. Of course, Zeno can erase anything or anyone, but he isn’t a combatant, leaving the Grand Priest the strongest warrior in the series. Nobody can stop him, even the Gods of Destruction and their Angels.
We can say that because of him, Zeno is quite the spoiled brat, getting everything, and doing anything he wants. This gives rise to an interesting question that might explain everything about the Tournament of Power: why is the Grand Priest stuck babysitting Zeno?
The Grand Priest is so powerful, he can do the thing in the image below at anytime he wants. It’s also possible that him and his children isn’t erasable, as to why they are also irreplaceable in their duties. He also seems to be more powerful than Zeno’s guards. Is it because he doesn’t want to take the position of being the King of Everything? Or is he stuck being Zeno’s attendant?
The last one is the most likely reason. What if the Grand Priest was actually an enemy, before Zeno was the King of All? The previous King might’ve seen the damage the Grand Priest will bring to his successor. In a way to defeat him, and also preventing him from making any future damage, the previous King cursed the Grand Priest to be the all around attendant of the next King, which is Zeno. If he failed or tried to break the curse, he will just disappear.
This might also explain the reason why the Grand Priest hates the idea of the Tournament of Power. You see, even though he’s cursed to babysit Zeno for all eternity, he’s actually in a great spot right now. He’s also the only person that Zeno listens to, except Goku. Because of this, he’s actually the de facto rule of the Multiverse. And he doesn’t want any mortal to take that from him just by impressing the Zenos.