Cult classic PC game Dungeon Keeper is free to download on PC.
EA's made the game free to download as part of its Origin On the House promotion (it usually costs Ł4.25).
Now, this Dungeon Keeper is the good one, the one made by Peter Molyneux's Bullfrog and released in 1997. It is not the bad one riddled by microtransactions that came out in 2014.
Rick Lane wrote about the original Dungeon Keeper for Eurogamer back in February, if you're wondering what all the fuss is about.
Or, you could watch the video below, in which Ellie Gibson plays Dungeon Keeper with not Peter Molyneux.