Keldeo

How Keldeo joined the Tourney
Long ago, a fire started in the Moor of Icirrus because of a war among people. In this fire, Keldeo was separated from its parents, but together, Cobalion, Terrakion, and Virizion took care of Keldeo. They acted as its parents, and they taught it knowledge and moves for survival. Keldeo eventually grew and even surpassed the three Pokémon. One day, Keldeo took off from the forest with no one knowing why.

When the four meet again, they teach Keldeo the move Secret Sword.

How to Unlock
The player must complete one of the following requirements to unlock Keldeo:
 * Play 180 Matches in the Versus Mode.
 * Beat Classic-Adventure Mode with Cobalion, Terrakion and Virizion on Hard difficulty. For both of these options, the player must brawl Keldeo on the Pokemon Stadium IV stage. After defeating Keldeo, the announcer will say "Someone else has joined the Tourney!" after a Smash Ball appears on the lower-right corner of the screen with a message saying "You can now use the last of the Swords of Justice, the young Keldeo!".

Sacred Sword
His signature move. Keldeo slices the foe with a long horn.

Take Down (Side)
Keldeo charges up, then does a dash attack with his horn.

Aqua Jest (Up)
Keldeo surrounds its entire body with water and goes straight upward.

Aqua Tail (Down)
Keldeo sticks its tail out and a spiral of water spins around it.

Hydro Pump (Hyper Smash)
Keldeo shoots a large water beam from his mouth

Secret Sword (Final Smash)
Keldeo charges up, runs fast, then impales the opponent's chest with his long horn.

Trivia

 * His english voice shares with Finn the human
 * Keldeo's rival is Shroob.