Genre[edit]
Realms of Darkness is a hybrid between a role-playing game and adventure game.
The two characteristics that a role-playing game and an adventure game have in common are: (1) text rich and (2) freedom of exploration. Then, a specific characteristic of the former is that player characters earn permanent upgrades (usually regulated by experience points). Instead, a characteristic of the latter is that it features complex puzzles and interactions with the in-game environment. Furthermore, at least at the time of the release of Realms of Darkness, a text parser was an exclusive province of adevnture games.
Realms of Darkness features all the aforementioned characteristics, therefore it can be ascribed to both genres at the same time.
Similar games[edit]
From a role-playing point of view, Realms of Darkness stands between The Bard's Tale (released two years earlier) and Advanced Dungeons & Dragons: Pool of Radiance (released the following year). The dungeon floors are smaller and richer in content than the ones featured in The Bard's Tale; the combat system, too, draw clear inspiration from that game. Classes and level-up system are closely reminiscent of the ruleset of Dungeons & Dragons, instead.
It looks like Strategic Simulations took the combat system from Wizard's Crown (1985) and integrated it into the gameplay of Realms of Darkness in order to obtain the Gold Box engine.
From an adventure point of view, we should look at games with a text parser from the same years. For example, the extra-famous Quest for Glory series started just two years later.