When it dragged me down to eat me. [Or part of him, anyway. It doesn't matter when it comes to how he experienced it.] It was all--slippery. In and out of reality. Not like me, I understood that, I understood how I was working, but it was-- I don't know what it looked like, but I saw it, and it, it was, I don't know--

[Sans goes rigid again. He saw it, and even scraping at the barest outlines of comprehension had driven him into senselessness, and he can remember that. Black tentacles and chanting he couldn't stop. He's dizzy and shaky just thinking about it. If he keeps thinking about it is it going to happen again? He needs to stop thinking about it. He needs to stop, but he can't, he can't do anything--]