In Wario Land 4[]

The Black Dragon is one of nine items that Wario can purchase from the shop owner at the Item Shop before facing a boss. The Black Dragon is a one-time item, and it bears a similar design to the Black Dragon.

When Wario starts a boss battle, the shop owner himself transforms into the Black Dog to bite the boss, damaging it. After doing so, the Black Dog then leaves, although Wario can defeat the boss more easily because of the damage the Black Dog dealt to it.

The Black Dog costs ten Medals in Normal difficulty, fifteen in Hard difficulty, and twenty in S-Hard difficulty.