| Qralloq |
It's a cool idea, particularly the goblin aspect. In many cultures, gods were simply ascended mortal heroes/villains and not omnipotent omniscient, which is kind of what Q is more like, but if you can tone it down you may be able to retain that "agency" aspect. I've personally been subverted by over zealous DMs and their in-game god egos and really I just stopped showing up. If I wanted all my actions to be irrelevant, I'd read a book.
But, if the players can subvert the Q, then there you go. In fact, pulling one over the immortal could be very rewarding. Just make sure that the immortal doesn't always win, or always see through the players schemes.
Check out Faiths and Pantheons, or Dieties and Demigods from the previous D&D systems for an idea on how powerful the top dogs are.
And for your players sake, make all of the immortals actions game-mechanic explainable, even if you don't explain the mechanics to your players.