Bloody goddamn hell. More or less fatfingered a zerg potion. Promptly panicked, didn't want it to go to waste (currently don't have the sludge to make another), only one thing I could remember wanting to farm... an obsidian rose.
So, of course, I immediately jumped down the hellavator. Way down was mostly uneventful except roadkilling something I didn't notice before it died and spending some time in a place or two goomba stomping something that had managed to jump in below me.
Exit was hopy shit levels of congested -- I had used that instant hellavator thing to make it, so the side exits were only the 5 tiles high or so I dug out the 1 tile thick wall. They were buried in slimes, bats, imps, three or so bone serpents humping the land trying to get to me, etc. Digging out further up was a joke, as everything above those entrances were basically layered in flying enemies. Demons, more bats, those gluttony things, crap falling in from the caverns above, so on. Normal zerg rush environment, basically.
Now, I try to clear enough space to get out (I've been constantly forgetting to get a knockback canceller, so I couldn't just walk out and tank it very easily). This actually lasts for a bit, as I had done up the surroundings pretty well to prevent voodoo trigger, and eventually my summons manage to stop humping the wall and start woodchipping the mass of meat trying to agglomerate its way up to where I was hooked to the hellavator wall.
Amusingly enough, I'm pretty sure that's what caused what most reading has already figured out was going to happen. When my seven-ish stack of dank creeper and blood clot started chewing into the enemies swarming into the bottom of the hell shaft, slimes started dying so fast that, despite the fact most of the bottom and surrounding area were vented to let lava drain, lava was not just collecting but rising up the hellavator by sheer dint of collective slime death. And, of course, spreading its way into the surrounding area.
So said obvious thing happened. Something killed a (okay, probably several between the point the first appropriately placed one dropped the doll and it landed, the spawn rate was actually more than just the 30x zerg effect) voodoo demon. The slime genocide got its last laugh, as I then got to experience the wall of flesh, mid zerg rush, with it starting with me still inside the hellavator, without knockback immunity, unwilling to cancel the potion effect, and the exits (and land outside, and air, and ceiling, and...) buried in things that wanted me dead.
Not only was the wall coming with its normal stuff happening, most everything between ceiling and floor (and below floor) was covered in so many enemies it was like there was another wall of flesh in front of the other, except made out of demons and bats and shit. Extra fun bonus points, the direction the wall was moving? I hadn't explored more than like a half a screen or so, yet, and I had no intention of freezing my health and shitkicking things that way.
So yes, vulgarity started flowing copiously as panic mode left easy modo 30x spawn rate and went into extra hard, I jammed my character into the mass of death (which ate about half my 424 health even with a 100 point heal) and did my damnedest to flee and chuck whatever I could in the other direction.
Now, no spoiler here, this ended with my ass hella' dead. Despite everything I made it past three buildings and a hill before the last bit took me. What was pretty goddamn amazing, imo? Wall's HP at the end, expert mode and all? 366. I almost got the blighter even though my total prep was farm proofing going the wrong direction, whatever crap I was carrying at the time, and a knee-jerk jump into the hell hole after forgetting the all buffs button includes the zerg potion.
Overall, even dead as hell at the end of it, the experience was pretty damn great. 9/10, would panic jump my way face first into a 30x+ spawn rate pre-wall hell again.