Dungeon Synth is a subgenre of dark ambient music that emerged in the late 1980s and early 1990s. The genre employs aesthetics and themes typically associated with black metal and applies it to dreamier ambient songs.
Dungeon Synth uses many aspects of black metal in its visuals. A lot of the members of the genre use corpsepaint and dress in medieval clothes. The album artwork also uses medieval-style paintings.
Deja Vu - Mort Garson, most popularly known as the theme to The Adventure Zone, a podcast created by the McElroy family following their D&D campaign. This song is an example of Dungeon Synth because of its combination of fantasy-esc (high wandering melody, like what you would hear on the soundtrack of a fantasy movie, emphasized by its use in a D&D podcast) and rock elements (good baseline, synth instruments).
The Dungeon Synth Archives - YouTube, A YouTube channel dedicated to reposting Dungeon Synth gems.