Alcahest is a 1993 action game developed by HAL Laboratory and published by Squaresoft for the Super Famicom. It is one of the titles Square did not develop but did publish. Controlling the swordsman Alen, who embarks on a journey to stop the demon tribe led by Babilom, an emperor planning to conquer the world with his imperial army and the titular demon god who revived from his previous defeat a thousand years ago, the player explore and search for items to progress and power-ups, fighting bosses and minibosses. During gameplay, Alen meets Guardians that aid him with their power, and allies that join him along the way.

First announced in 1992 under the tentative name Guardian Blade, Alcahest was created by HAL Laboratory, known for their work on the Kirby franchise. It was directed and designed by Atsushi Kakuta, with late Nintendo president Satoru Iwata serving as producer. The music was composed by Jun Ishikawa, known for his work on the Kirby series. The game was supplemented by a strategy guidebook. Though it was not officially published outside Japan, an English fan translation was released in 2002. It never received an official soundtrack release unlike other Square titles, although its main theme was included as part of a compilation album published in 2017.

Alcahest was well received by critics who reviewed it as an import title; praise was given to aspects such as its graphics engine for eschewing the super deformed style prevalent on Super Famicom, intuitive controls, blend of action and role-playing elements, the variety of partners, diverse and flowing level design, simple but dynamic arcade-style gameplay, accessibility due to the light use of Japanese and challenge. Reviewers also noted that the game's style and combat system were reminiscent of Zelda and Soul Blazer, but most felt mixed regarding the music, while criticism was geared towards its puzzles, lack of proper character interaction, short length, scenario and repetitive dungeons.

Alcahest is an arcade-style action game with RPG elements, that plays from a top-down perspective similar to titles like The Legend of Zelda and Soul Blazer, in which the player assume the role of swordsman Alen embarking on a journey to stop the demon tribe led by Babilom, an emperor planning to conquer world with his imperial army and the titular demon god who revived from his previous defeat a thousand years ago. Prior to starting, an options menu can be accessed at the game's title screen, where any of the four available difficulty settings can be selected or change the controls setup. The player traverses through eight stages, populated with an assortment of enemies and obstacles, that are progressed by finding items and power-ups that aid Alen on his quest. Every stage has bosses and minibosses, which must be fought in order to progress further.

Alen is capable of attacking enemies using a blade bestowed on him by the Guardians; After specific boss fights, the player gains the abilities of one of the four Guardians (based on the four classical elements). Alen can also charge his blade for a special attack, which differ depending on the elemental Guardian selected. MP is used to summon Guardians in battle. The player can swap between each Guardian by pressing the shoulder buttons. Alen can also perform dash attacks when running by double-tapping the d-pad, as well as block projectile attack by standing still with his shield. Along the way, Alen meets five allies that join him at predetermined points of some stages. They are the young wizard Garstein, the princess Elikshil, the knight Sirius, the android Magna and the shape-shifting dragon goddess Nevis. Though they cannot be controlled directly, allies attack and use special moves when the corresponding button is pressed. "Special Points" (SP) is required for a partner's special attack.

Alcahest employs a checkpoint system where the player will start off at the beginning of the checkpoint Alen managed to reach before dying. Alen's vitality decreases when attacked, but is increased at the end of each stage. Certain items found on each stage restore Alen's status. Once Alen's vitality is depleted, the game is over. Alen gains experience points (EXP) by defeating enemies and bosses. After gaining a certain number of experience points, the player earns an additional continue to keep playing. The player is given passwords at the beginning of each new stage.