Play a warlock character who calls himself Vithimorex or something like that. Always mention how grateful you are to your patron, Frank, for the wondrous powers he gives you.
Slowly reveal that the powers you get from Frank are things like “sense of smell” and “verbal communication”. As it turns out, Vithimorex is an extradimensional Thing possessing the person formerly known as Frank. All the eldritch blasts and shadow conjurations are boring powers according to Vithimorex. He can’t wait for the level 14 ability to understand and appreciate music.
Also, I realized something about the name I made up, so here’s a song:
When the moon splits in two and your nightmares come true, Vithimorex...
When the world seems to bleed since the dead god was freed, Vithimorex...
That is definitely a fun RPG idea