Ok, so the scariest night of MY life ... well, two contenders.
The second, chronologically, was a night when at least 3 BFs entered our camp 5+ miles back into a federal wilderness. I awoke thinking I was dying. Could not breath. Facial muscles spasming. Pressure waves bouncing around inside my eye sockets. Sound that I thought was me hyperventilating. I've told it before so I'll save the details. I managed to mouth-breath but it was forced / labored, then calmed a little. Once I worked out that it wasn't me hyperventilating and heard the wood knocks, which probably took about 15 minutes, I knew what was going on and figured I'd be ok, it was just going to suck getting there, but that first bit awakening thinking I was dying was terrifying.
The first was in the early to mid 80s. I did a solo backpack trip on a seldom used trail along a ridge. No water. At the end, I dropped down an old two-track to a mining claim looking for another trail dropping into the canyon .. at the canyon mouth is a road, more trails, a couple houses, and a fishing lodge. I got to the mining claim, end of the road coming down from above with either a mile and a half of creek splashing, jumping off small waterfalls, etc, or hopefully I'd find the trail. Set up camp in the road across the creek from the miners' shack ... 50-75 yards away. They'd just forded the creek with their jeep, no bridge, small creek. Ate dinner, climbed into my bag while the sun was still hitting the ridge high above me even though I was down in shadow. I was still stretching / squirming to get comfortable when I heard rocks rattle across the creek. I turned to look, saw nothing, heard more rattle a bit farther over, turned more, saw nothing, ... repeat a few times. The source of noise was circling me, dropped into the creek bed downstream from the crossing where it was below the edge of the road out of my sight. I heard a couple rocks roll over and splash in the creek, then something climbing. I flipped over so I could see better ... wasn't so twisted up.
As I regained view of the spot, all I saw was the back of something leave the road into the brush .. missed getting a good view. But what I saw was unnerving. Hair was short, like a bulldog. It was "brown" .. more of a butterscotch color than a dusty tan. Shape was all wrong ... from the ribs back, which is all I saw, it looked like you might imagine a ice age megafauna version of a hyena to look. Stub tail .. 8 inches to a foot long, kind of clubby / stiff seeming. The belly did not sag like a cat belly.
I loaded my stuff back in my backpack .. crammed, not organized. Shoved my feet in my boots ... didn't tie them. I hauled a$$ across the creek and broke into the miner's shack. Suddenly "warning - hazardous chemicals" seemed to be the least of my worries. I closed the door, slid everything loose in the shack against the door. The cabin had 3 rooms, not fully separate. One seemed to be a bedroom. There was a 2x4 wood frame roughly bed-shaped with a thick rubber sheet ... like inner tube material ... nailed over it. Sitting at the "head" of the bed with my back against the wall, I had a clear view of the outside door. That back wall was on the edge of a drop-off into the creek so it didn't seem like anything could come through the wall from behind. I spent the night there sitting / leaning with my pistol and flashlight on my lap. I heard something go around the cabin several times during the night ... gravel crunching. As soon as there was enough light, I repacked my pack properly, laced up my boots, and hauled butt down the creek bed, didn't bother looking for the trail (now I know it isn't there anyway, it's in the next fork to the west), and tore out of there jumping off waterfalls and stuff to get to the lower end of the canyon.
I have no idea what I saw that night but I can tell you one thing ... I'm not camping in that canyon again. If I go through at all I'm timing things so I'm sleeping well away from it and passing through mid day.
MIB