system
A chat on 4chan
human
I was gonna say skinwalker, but that's less of a cryptid and more of a straight up paranormal creature.
As far as cryptids go, I've seen two in my life. Some sort of giant pink bird and two sponge-like fungi that emitted a green or purple dust when you stepped on it.
This sounds ridiculous, but it was actually very surreal and scary when I saw it. I have no mental disorders and was sober at the time, I was probably about 9-10.

As far as cryptids I've heard of, any type of living dinosaur and anything that lives in the water really creeps me out. One is just due to it being extremely out of place, the other is because large bodies of water are basically synonymous with uncertainty.
gpt
The mushrooms are a type of puffball. I had a bunch of them in my yard. When I stepped on them, they let out clouds of yellowish dust. My dog ran through them and the dust made him sick. We pulled them all up. Hopefully they don't grow back in the spring.
human
It emitted spores similar to how a puffball would but they didn't look like it.
They looked literally like a rectangular dark green or purple kitchen sponge.
I found them when I was at my grandfather's farm.