Just beat the game on Normal (was really lucky in Caves and one of the demons dropped Gotterdamerung) and wanna move on to other difficulties, but there don't seem to be any?

Am I remembering things wrong? Were the difficulties a Hellfire thing only? If so, can my character be imported to Hellfire without losing my gear?

There are difficulties in Diablo - if you play multiplayer. If you play single player, then no, there is no official way to get difficulty levels. There is a bug that can give you most of the effect though.

Yes, you can import a character into Hellfire. You will lose all your items in the transfer though.

20 years ago is a long time but as I remember it you can get a single player game into a higher difficulty by first launching a multiplayer game at that level of difficulty. I'm sorry but I don't remember any further details on the matter.

That is stupid PSX version had Nightmare and Hell

The psx version basically only had multiplayer.

Next version of devilutionX will have difficulties for single player. I expect we will release it by the end of the month.

Hmm you actualy right when i think about that. Also you could save character and that was OP but understandable.
Full save took about 6-8 slots maybe 9 (not sure, long ago) but character safe just 1 slot. You could duplicate gold thanks to that, 2 chars two saves. Nvm i digress alot. :D
Gonna try the hellfire then. Have a good day.

As I remember it one can play a Diablo single player game at Nightmare or Hell difficulty if the single player game is started after exiting a multi-player game of the desired difficulty level. Once one has done that and saved the single player game (now at Nightmare of Hell difficulty) the difficulty level persists for that game.

It doesn't persist, you will have to do the hack before loading the game or you will get a hybrid where the monsters that where active during the save are the higher dificaulity but drops and everything else is normal.

Is there any way you could add a 'Hardcore' mode like Diablo 2? That'd be freaking sweet in SP and MP.

I know but it doesn't delete your character like D2, so you can just reload the save.

Right, but you don’t reload, because you’re *hardcore* like that ;)

I'm a weak, weak man. Temptation is too great not to reload it. I need spanked.