The Dark Emperor (全てのやみの王, lit. "King of All Darkness") is a character from the Find Mii series. He is the final boss of the Secret Quest for the game Find Mii 2. He appears as a stage hazard on the Find Mii stage in Super Smash Bros. for Nintendo 3DS.
The Dark Emperor will come onto the Find Mii stage occasionally and use a random magic and color, which affects characters of that color, such as giving them power boosts or lowering power. The magic's effect is shown on the lower screen. If the Dark Emperor comes into the foreground, players can attack it, but touching the Dark Emperor deals slight damage and knockback. If it is defeated, then the player who defeated it will get a stat boost. Sometimes it can destroy one of the two platforms. If players launch the king's cage away, the Dark Emperor will leave temporarily to retrieve the king.
This enemy brings chaos to the battlefield, employing three different attack patterns. He'll use magic to help--or hinder---fighters depending on their color. He will also smash platforms with a localized earthquake. Last, he'll directly strike fighters. Wait a sec... What a cheater--he's invincible when he's in the background!