Let this man rest in Gods name." @Ajoshy_u, "No specifics. Just general talks as usual. No data to back up promises. Speech full of blame. Maybe someone can help explain better. Please."
In the book of Exodus, we read the epic story of God's power to free his people from slavery. In chapter 14, we get to the climax ofthe story: the crossing ofthe Red Sea.
To control the Abyss is a startling feat even for gods and other beings of immense power. These two have not yet appeared in D&D 5e, but an enterprising DM could easily use the stats from another extremely powerful creature.