First of all, thank you for playing!
This game was made a jam submission so we didn't have time for a traditional final boss as we would have liked. You get a score at the end based on your remaining health, oil, and sanity which all deal "damage" to the skull. Your total score across all runs should be visible in the starting room after you have completed a single run.
Once again, thank you so much for playing! Great work at beating the game!