Castle of Dragon, known as Dragon Unit (ド ラ ゴ ン ユ ニ ッ ト) In Japan, is a side-scrolling action game developed for arcade by Athena Co. in 1989, and later ported to the NES in 1990. The game was published in Japan by SETA Corporation, and in the United States by SETA U.S.A.
The goal of the game is to fight through a number of monsters using the sword and shield. The protagonist (different depending on the version) can acquire armor that keeps them alive longer, and will slowly lose pieces of it as they take damage. Players can also find upgraded weapons that do more damage or have longer reaches.
The game was followed by Sword Master, an NES exclusive.