The Black Jewel is the main antagonist and the final boss of the game Wario World.
The Black Jewel, at one point, was stolen by Wario and was kept in his castle in the treasure room. The Black Jewel eventually broke out and turned all of Wario's treasure into monsters and destroyed his castle in the process. Wario must go through a long journey to gather all of the boss keys to unlock the treasure chest and reveal the Black Jewel. The Black Jewel was eventually defeated by Wario and his treasure was restored.
In battle, the Black Jewel only uses two attacks. It's main attack involves shooting a stream of fire out attempting to trap Wario in the walls of fire. If the Black Jewel succeeds in doing this, it will launch rainbow-colored shockwaves at Wario that can deal high damage. The Black Jewel has a total of eight lives and it's attacks get more faster the lower it's HP is.
The main key for winning the battle is for Wario to break all of the crystals containing Spritelings surrounding the battlefield. Wario should stick to dashing as not only it will break the crystals, but also help avoid the Black Jewel's fire wall attack. If Wario does get boxed in, he should move around and jump to avoid the shockwaves. Once all of the Spritlings have been freed, they will attack and stun the Black Jewel giving Wario the chance to use a Mad Move on it (preferably the Piledriver).