Govellius for Sega Master System. Anyone hear of it?

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My brother use to play Govellius for the Sega Master system. It was too complex of a game for me at my age so I never played it. I still remember the music and the bosses, and the enviroments. But I have never met one person that has heard of it! It's kind of like a Zelda game, but for the Sega Master System. Are there any video games that you once played or watched someone else play, that has been lost, and no one you met since ever heard of it?