Secret Sword is the signature move of Keldeo. This move can be learned by via tutoring when the three musketeers; Terrakion, Cobalion, and Virizion are also in the party. It is weaker than its counterpart, Sacred Sword.
Secret Sword inflicts damage. Although classified as a Special move, this move calculates damage using the user's Special Attack and the opponent's Defense stat.
The user cuts with its long horn. The odd power contained in the horn does physical damage to the target.
Secret Sword is a move that only can be learned when the muskeeters are in the party.
Secret Sword can be learned if the muskeeters are taken to Moor of Icirrus.
When Secret Sword is used, it appears as if an invisible muskeeter trio joins in on the fight.