Jen is the girlfriend of a metal rocker named Lewis, who have both been through rough times in the past together. A strange and powerful creature attacks Lewis after a concert and runs off into the night with him, leaving Jen injured and near-death.

Jen meets a short gargoyle named Scree, who informs her that she must leave the physical plane Mortalis and accompany him to the demon plane Oblivion. The creature who kidnapped Lewis and left her for dead is an agent of Abaddon who represents Chaos and has been locked in struggle for aeons with Arella, representing Order. The balance between Chaos and Order has been upset and it is Jen's task to restore the balance, all the while hoping to discover the whereabouts of Lewis.

Primal can be described as a "3D platformer", being somewhat similar in its basic gameplay mechanics to Tomb Raider games. Puzzle-solving and action-based combat constitute the focus of the gameplay. The player can switch between Jen and Scree at any time; Jen is capable of fighting, but Scree is invulnerable to enemy attacks. When Jen is incapacitated in combat, Scree must quickly restore her to life within a time limit; failure to do so prematurely ends the game.

Combat is heavily based on "finishing moves" and Jen's ability to transform into demonic forms. There are four demons Jen can merge herself with; they are obtained one by one as the game's narrative advances. These demonic forms allow Jen to use special abilities, which include jumping to extreme heights, unnaturally fast swimming, slowing down time, and using powerful weapons.