The Black Rabite or Grim Rabite is a black or dark-furred Rabite occasionally encountered in the Mana series. It is typically a paragon of the Rabite species as a whole and acts as a megaboss in Seiken Densetsu 3 and a special upgrade monster in Sword of Mana. It is hard to find or unlock, and has powers well beyond those of a normal Rabite.
Seiken Densetsu 3
Only approachable in the Duran/Angela storyline, the Black Rabite is an incredibly powerful monster, capable of high-level magic spells and absorbing Darkness-based attacks. It is popularly considered to be the most powerful adversary in the game, and arguably in the Mana series as a whole.
No official art exists of the Black Rabite.
Sword of Mana
The Black Rabites encountered in Sword of Mana are considerably less powerful than the one in Seiken Densetsu 3, but they are still far more powerful than their normal counterparts. They are unlocked by defeating 999 Rabites. The "defeat 999" process produces Black/paragon upgrades of all non-boss monsters, not just Rabites.
Dawn of Mana
In Dawn of Mana, the Black Rabite is known as a Grim Rabite.
Heroes of Mana
The Black Rabite is a hidden boss in a bonus mission, but unlocking him is almost as hard as beating him. He appears in a stage that is only unlocked after beating the game on hard mode, and even then he will not appear until you have sent 999 regular rabites to their deaths throughout the game.