Mike Singleton had written a fair few Spectrum games before Lords of Midnight, but nothing near as memorable or as complex.
With this game he created a whole new genre, fusing strategy and adventure together into a so called "epic" with a whole new system of graphics called "landscaping". The latter gave you the character's eye of the terrain rather than just a map view allowing you to see a long way in open spaces but in dense forests, mountains or hills you could be within a few hours of a vast army and not even know it.
Despite a plot that's a thinly veiled steal from Lord of the Rings it works spectacularly. You start with just four characters, but within a few turns you could be commanding an army of thousands. watch out though, as Doomdark's armies are much bigger than any you can hope to raise and only through superior tactics will you ever gain a military victory.
This is one of the most inventive Spectrum games ever made and, not surprisingly, one with the greatest longevity. If you've never given it a go, there's a bit of a learning curve to get over, but it's well worth the effort. Alternatively try the excellent remake; the Midnight Engine. There's also a multiplayer version, M/MU, for those who want to take it that bit further.