Astyanax is the NES port of a Japanese arcade game called The Lord of King. It is a side scrolling action game.
The plot for the NES version is different from the original arcade game. In the NES version Astyanax, a high school student dreams every night about a princess calling for help. He is summoned to the mythical realm of Remlia by a pixie named Cutie and asked to rescue Princess Rosebud from the evil wizard Blackhorn.
The game allows Astyanax to crouch, jump, attack, and cast the equipped magic spell. The game features a power bar, which when full, Astyanax's attacks are powerful, but when empty are weak. The bar empties with every attack and quickly refills.
New to the NES version the game allows the player to upgrade their weapon by collecting power-ups in the game. The second weapon is a spear, and then a sword.
Spells include: bind, which freezes all enemies on screen temporarily; blast, which shoots a multi-directional fireball; and bold, which attacks all enemies with lightning.
The game features 6 levels which can contain 2 stages, mini bosses and a boss.