Dragon Slayer IV: Drasle Family

Dragon Slayer IV: Drasle Family, known in the West as Legacy of the Wizard, is a unique action RPG for the Famicom (NES), developed by Falcom and released by Namco in 1987.

A family of four plus their pet set out to defeat the dragon Keela. Each family member has unique abilities, and you have to switch between them to explore a huge underground labyrinth and find the four crowns.

It is a hard but deep game that predates the metroidvania genre.