I've been theory-crafting this idea with my players for a while now and we wondered if it is possible for the DM to be a Patron for a Warlock. As far as I know, in XGtE it is written that you can create a custom Patron.
Is there a rule against the DM being an entity in the game which empowers a player (in this example a warlock) while being the DM in the same place (so they'd have two roles to play at the same time)?
Also we were wondering what special powers the player gets from his Patron. How does this interfere with the game itself?
But I guess that no Warlock Player wants to have their patron sitting OoC next to them.