If you're going to play the first game, and I highly recommend it, download and use the open source engine from https://keeperfx.net/. It fixes some bugs and stats from the original game and allows it to run on modern Windows systems in higher resolutions.
I loved this game since it was first released and it's voiced by Peppa Pig's Dad! š
Fun fact: in the DOS version, when you possess an imp, the only task you can perform is to mine, you cannot do anything more except attack. In keeperfx, you can grab corpses and take then to your graveyard, or grab traps and put them in place. I'm not sure whether you can put gold in your treasure room as well.
EDIT: it also fixes the bug when level 10 creatures use their speed spell, so it lasts until the end, instead of just 5 seconds.