Square（現今的 Square Enix）於 1986 年 9 月 18 日在任天堂 Famicom（紅白機）上推出《國王騎士》（King's Knight / キングスナイト），這是公司在開發《最終幻想》之前的早期實驗性作品，也是遊戲史上極為罕見的「橫向捲軸射擊 RPG」。以「一人失敗即全盤皆輸」的高難度設計，讓老玩家留下深刻而痛苦的印象。

在技術表現上，挑戰當時遊戲類型的界限。表面上看似射擊遊戲，但實際上擁有 RPG 元素，包括角色等級、生命值與成長系統。共有五個關卡，前四關分別控制四名不同的角色，以接力形式進行遊玩。音樂由日後《太空戰士 / 最終幻想》作曲大師植松伸夫創作，帶有宏大且悲壯的史詩感，即便在 8 位元音源下也十分突出。

劇情沿襲經典英雄傳說：奧爾提利亞王國的克萊雅公主被邪惡龍王博爾加拉擄走，四位被命運選中的勇者必須從各自的領地出發，穿越沙漠、森林、地下道與海洋，最終在龍王城會合，合力發動終極攻擊擊敗龍王，拯救公主。

操作上，與當時常見的射擊遊戲截然不同。背景中的牆壁、樹木甚至山脈大多可以射擊破壞，而這些障礙物下往往隱藏著提升角色能力的道具，如升級、跳躍力或攻擊力加成。每名角色都有自己的特色與挑戰：戰士雷傑克平衡型，從平原出發；法師卡利瓦擅長魔法彈攻擊，從森林出發；怪獸巴魯薩體力高但跳躍力差，從地下道出發；小偷托比速度快，從水域出發。最終關卡要求四位角色同時登場，若前四關有角色死亡或未收集到關鍵「四神器」，將難以完成最終關卡，玩家必須完美通關前四關才能挑戰結局。

市場評價方面，呈現兩極反應。評論家讚賞其大膽創新，將射擊與 RPG 系統結合，但難度極高，障礙物繁多、角色成長高度依賴記憶道具位置，使新手玩家難以應付。

歷史地位上，《國王騎士》被視為 Square 的小眾經典之作。雖然銷量不差，但其硬核設計讓它成為高難度遊戲愛好者心中的經典。此外，多年後在《最終幻想 XV》中，主角們最愛玩的遊戲之一，正是虛擬化的《國王騎士》，彰顯它在 Square 玩家心中的持久影響力。

Square (now Square Enix) released King’s Knight (キングスナイト) for the Nintendo Famicom on September 18, 1986, as one of the company’s early experimental titles prior to developing Final Fantasy. The game is an exceptionally rare hybrid of side-scrolling shooter and role-playing game, and its notorious “one character fails, the entire party fails” mechanic left a lasting—if often painful—impression on veteran players.

Technically, King’s Knight challenged conventional genre boundaries of the time. While it visually resembled a standard shooter, it incorporated RPG elements such as character levels, health points, and growth mechanics. The game consists of five stages, with the first four each focusing on one of four heroes in a relay-like progression. The music, composed by the future Final Fantasy maestro Nobuo Uematsu, carries an epic and dramatic tone, leaving a memorable impression even through 8-bit sound hardware.

The story follows a classic hero’s journey: Princess Clea of the kingdom of Ortaria has been kidnapped by the evil dragon king Bolgarra. Four chosen heroes set out from their respective territories, traveling across deserts, forests, underground tunnels, and oceans. Their ultimate goal is to reunite in the dragon king’s castle and launch a final combined attack to defeat Bolgarra once and for all.

Gameplay deviates from conventional shooters of the era. Nearly every part of the environment—walls, trees, and mountains—can be destroyed. These destructible objects often conceal items that enhance character growth, such as level-ups, increased jump height, and stronger attacks. Each hero has unique strengths and challenges: Rayjack the warrior is balanced and starts on the plains, Kaliva the mage uses magic projectiles and starts in the forest, Barusa the monster boasts high HP but poor jumping and begins in the tunnels, and Toby the thief is fast and agile, starting on the water stage. The final stage is particularly brutal: all four heroes appear simultaneously, and if any hero has died or if key items (the “four sacred artifacts”) were not collected in earlier stages, the ending becomes nearly impossible to complete, making perfect execution essential.

Upon release, King’s Knight received polarized reception. Critics praised its daring innovation in merging shooting and RPG mechanics, yet many players found its difficulty intimidating. Obstacles could easily trap players, and character progression relied heavily on memorizing item locations, which made the game extremely unforgiving for newcomers.

Historically, King’s Knight is considered a cult classic and one of Square’s “hidden gems.” While not a commercial failure, its punishing difficulty made it niche. Interestingly, in Final Fantasy XV, the protagonists’ favorite in-game pastime is a virtual version of King’s Knight, highlighting its enduring legacy among Square fans.