the green flag, click it in the story after you defeat exilamon and moradramon joins your team, you go through a bunch of other stuff and the you see De-metal expecting you, after a long lecture, he will turn into the thing you see in the background, and he is the hardest boss you will ever fight, the kind of boss that will heal when you just need one more hit.
music By Undertale Vs Alphys remix DO NOT! COPY OR STEAL THIS ART
