Dragon Slayer IV: Drasle Family (ドラゴンスレイヤーIV ドラスレファミリー), released as Legacy of the Wizard in the United States, is a fantasy-themed action role-playing platform game released for the MSX and Famicom in Japan and for the Nintendo Entertainment System in the United States. Dragon Slayer IV is an installment in Falcom's Dragon Slayer series, and one of only three Dragon Slayer games to make it to the United States. The game was an early example of an open-world, non-linear action RPG, combining action-RPG gameplay with "Metroidvania" style action-adventure elements.

The Worzen family consists of six members of three generations, plus the family pet, which resembles a small dinosaur. The player takes control of the members of the Worzens and their pet, sending them one at a time into the vast underground cavern filled with traps, puzzles and monsters, in search of the four crowns, while periodically returning to the family household on the surface to change characters and to obtain a password. Each member of the family, which consists of the father, mother, son, daughter, and the pet, has different strengths and weaknesses to contribute to this goal. Some characters have seemingly powerful strengths, but each is offset by proportionate limitations. For example, the father has the strongest attack power, but cannot jump as high as the rest of the family. The mother of the family has relatively weak attributes, but is the only one who can use specific magical items required to find one of the crowns. By discovering and utilizing each character's strengths, the player travels through the extensive dungeon, eventually fighting four bosses to gain the crowns.

The game's vast labyrinth has five major sections, four of which contain a boss who guards one of the crowns, and the fifth which contains the final boss. Each section has noticeably different characteristics and different background music, and was designed with one particular playable character in mind. The crowns cannot be acquired without the player utilizing the family members' specific skills to get through the sections of the dungeon. Therefore, each playable character must be used at some point in order to complete the game. For example, one section may be blocked with bricks that can only be destroyed by the mattock, so the player must use the character who can use the mattock to get through such an area. After all four crowns have been acquired, the family's young boy can use the magic of the crowns to find the Dragon Slayer, and then use the magical sword to slay the evil Keela.

As the player runs through convoluted passageways, he will encounter an endless supply of monsters. Each character can fire shots of varying strength to defeat these monsters, but attacking uses up the character's magic power. Most of these monsters drop items when defeated, such as keys which can be used to open locked doors and treasure chests, bread which restores the player's health, potions which restore magic power, and sometimes poison which harms the player. Money can also be collected from defeated monsters, and then spent in shops and inns located throughout the dungeon.

The characters in Dragon Slayer IV must utilize several magical items in their quest. These can be acquired from chests or bought in shops that are sometimes located in very impractical locations. Item effects include restoring the character's health and magic power, boosting attack power or range, or environmental effects like enabling the character to fly or move special bricks. Some items can only be used by certain characters, and since accomplishing the goals requires the use of these items, it is up to the player to determine which character must be used to regain each crown. Acquiring these items and finding how to properly use them is the essence of Legacy of the Wizard.