Thread:Vorknkx/@comment-3547390-20150204202730/@comment-1496755-20150427101637

Only PoP has a Nightmare portal (classic Hexen II doesn't). It's hidden somewhere in the first level. There is a nasty little puzzle you need to solve, in order to get a key (you have to be playing on the hardest difficulty available from the menu, otherwise the puzzle is inaccessible). But the game doesn't tell you where to use that key - it's a locked door that doesn't display a "you need a key" message when touched, so you have to figure it out. And if you succeed, you'll get a ring of flight, so you'll have to know where exactly you have to fly with it. If you do, you'll find an incospicuous wooden door... and beyond it lies Nightmare difficulty!

(make sure you've upgraded with the 1.12a patch because it fixes a few bugs related to Nightmare)

Indeed, it's a lot more complicated than finding these portals in Quake and its mission packs.

PoP's puzzles are easier, I think. The only exception is that thing with the prayer wheels, where you either have to write stuff down or memorize it (I've done it both ways). It's still less painful than Hub 3's constellation puzzles (ouch!).

Those snowy environments are amazing. And the snow falling from the sky is pretty convincing too.