The First 15 Minutes of Evolution: The World of Sacred Device (Dreamcast)

Coped from MobyGames:

Mag Launcher is the only child in a legendary family of adventurers. Several years ago, a cute little girl showed up on the doorstep of the Launcher house, holding a letter from Mag's father, who had went long ago on another dangerous adventure, and hadn't returned since then. In the letter, Mag's father asked him to protect the little girl (named Linear Cannon). Since then, the two children have been living together in the Launcher house. Mag's father never came back...

One fine day, the 8th Emperial Army arrives at Pannama town, in search of an artifact called Evolutia. Mag remembers that was the very same artifact his father had been looking for...

Evolution: The World of Sacred Device is a RPG with a heavy emphasis on dungeon exploring. Mag and his party (Linear, the butler Gre Naid, and two other adventurers), explore dungeon after dungeon, searching for the mysterious artifact. All dungeons are randomly generated. The combat is turn-based. There are mechanical devices called "Cy-Frame", which can be attached to the characters and make him (or her) perform special attacks of various kinds.