They're big, they're bad, and they're... purple!
You meet the Giant Purple Mutant Hellbeast (aka Barney on Steroids) for the first (and hopefully last) time on Warning: Earthquake Zone. He's totally immune to all attacks and basically you have to "leg it" to survive.
If you happen to return to this level after you survive the last level you'll find a little surprise. Barney has multipled. Not one, not two, but three Barnies may be waiting to greet you. Not only that but they are no longer restricted to the last room. You'll find them wandering around right at the very beginning of this level.
Note that Barney doesn't always appear if you go back down to Warning: Earthquake Zone, as this comp.sys.mac.games post reveals.
But why would you want to go back down through "Warning: Earthquake Zone"?
Well there are a number of reasons:
Given that Pathways Into Darkness allows you to move freely between most levels you might think that it would be possible to correct any of the above mistakes by going back down again. If you try however you won't get far.
It is possible to trap the Barnies behind a closing door. And you can pass the Green Oozes again by poisoning yourself provided you have that 2nd Thick Brown Potion. But all this effort is to no avail since one vital exit door is locked! Pity really.
But then there is always the Easter Egg.