Eternal Knight is a player vs. environment survival horror game based in a fictional medieval universe where players use daggers, swords, shields, bows, and magic to progress through a variety of aggressive and challenging dark fantasy enemies. The world of Eternal Knight is vast and consists of many unique environments including castles, dungeons, forests, jungles, marshlands, fortresses, ruins, sewers, towns, and villages all connected together in a Metroid-Vania style of layout. The combat in Eternal Knight has a high level of difficulty, the world and creatures within are set in dark fantasy, and the story is told almost entirely through the use of environmental storytelling.

The game focuses on exploration, RPG character upgrades, and challenging enemies with many secrets and optional areas allowing players to choose how long they stay in an area before progressing. The world, game mechanics, and enemy AI have all been designed around the different types of magic spells players can acquire. There are three categories of spells including offensive, defensive, and support allowing the player many different options on how to attack and defend against these enemies and in exploring the environment.

The following are some notable ways that Eternal Knight differs from the standard Souls-like genre: player vs environment focus allowing for offline exploration at your own pace, players receive more pronounced increases to stats when upgrading their character, death and combat mechanics designed to be less punishing to players, enhanced re-playability with a new style of New Game Plus, and greater dependence on magic allowing players to rely on ranged combat in all encounters.