Nox Arcana/Midnight Syndicate
I put these two in the same grouping because I feel that they are working in a similar fashion (and also sound very similar). The works by these two groups can be described as tabletop RPG and haunted house music. The sound is often nearly identical to dungeon synth, being fairly simple compositions done with keyboards, and with a focus upon darkness and fantasy. The reason why I do not include them on the list is that they are often somewhat too orchestral sounding, and I feel that they also lack a certain seriousness that dungeon synth has. Even though dungeon synth is often "hokey" because of that seriousness, the style of these two artists is hokey in a different sort of way, the intent being more to provide an atmosphere for fun. And then, there is the simple fact that these artists seem to have no connection or influence from black metal or dungeon synth musicians. I think it is from black metal that dungeon synth brought the grandiose feelings of "high art," the "No mosh, no core, no trends, no fun" attitude, which I feel these artists lack. It seems like these artists come strictly from the film and video game soundtrack tradition, while I think dungeon synth arrives somewhere pretty distant from such sounds. Still, I recommend both of them, as they make for very entertaining listens (and are incredibly useful for things like D&D).
I included both of these this time because not only do they have an extremely similar sound, but the same man is behind both of them. I love these projects. The atmosphere is earthy and archaic, a ghostly journey into a dark, fantastical, and mysterious past. It's rare that it ever really has the "dungeon synth sound," since it makes use of tribal-type percussion, many seemingly non-electronic instruments, and samples more reminiscent of world music, not to mention that the production values are much more professional sounding. But the reason why I include them in this post is because I feel that most of the time the music has an atmosphere and intent that is identical to that of dungeon synth, just with perhaps more of a world and new age touch. I highly recommend the works of these project to anyone who's interested in this genre. It is very far from the dungeon synth sound, but I think it is absolutely successful in allowing the listener to escape to a mysterious and beautiful world of fantasy.
Die Verbannten Kinder Evas/Dargaard
I don't consider these groups (and a number of other similar groups) to be dungeon synth because I feel it is less about escape into fantasy, and more about wallowing in sadness. Also, the sound is simply more along the lines of neo-classical, largely because of the heavy use of clean singing. I'm not sure if there's a proper genre of this kind of music: dark ambient, darkwave, neo-classical, I don't know. I just personally feel that this isn't the same sort of thing as dungeon synth. Still, the connection to black metal, the treading in fantasy moods, and the heavy use of the synthesizer earn these kinds of groups recommendations to those who listen to dungeon synth. I must admit, I haven't given these artists nearly as much attention as they deserve, so I'd rather not say too much more about it and speak out of turn, but it is certainly important to point out how closely it often comes to the "dungeon sound."
This artist utilizes synths for fantasy soundscapes, though the reason that I don't include it on the list is that it is often more along the lines of sound effects and field recording type material, along with dialogue in fictional languages. When it does come closest to dungeon synth, it seems much more bombastic, orchestral, and even tribal. Za Frûmi tells various stories, of cults, vampires, orcs, etc. I'd say that it would be very interesting and perhaps even moving to any fantasy-minded listeners, though to me it really lacks the dungeon feel.