You cannot grasp the true form, indeed. If there's one thing people remember from Earthbound (also known as Mother 2), it's this creepy git. While he was the main baddy of the first Mother game, he certainly didn't look like the horrific spawn of Sauron and Nyarthalahotep you see before you. In fact, everything about him seems more disturbing than it should be:

From the boss music (if you could even call it that) to his attacks to what he says when you're fighting him.

And to think the game was so lighthearted before his arrival.

I think Josh Scorcher covered him in his YouTube channel.