The Key Sword is a golden blade consisting of a long handle and several gear-like parts, a red gem within a gear acting as a pommel, and a small golden spike protruding from the top of a semi-gear.
In the manga, Robelu transforms Xeno Trunks' sword into the Key Sword so that he can use it to keep the hell gates open. The Key Sword allows Xeno Trunks to resist the attacks of the brainwashed Chronoa, and after transforming into Super Saiyan 3 he uses the sword to free her.
During both the game and the manga, Xeno Trunks loses his Key Sword during the battle with Mechikabura at the summit of Mechikabura's Tower. In the game, the sword is later found by Xeno Bardock during his battle with Dark Broly, and he uses the sword to defeat the berserk Saiyan and free the Time Patrol from Mechikabura's void. In all versions, the sword is later retrieved by Chronoa, and fully charged by hero, Tokitoki and Demigra. The fully charged sword is used by Xeno Trunks as a Super Saiyan God to weaken Mechikabura, giving Chronoa the opportunity to seal him away.
- Key Sword (Full Charge version) – The Key Sword wielded by Super Saiyan God Xeno Trunks. After being fully charged by Chronoa, Tokitoki, and Demigra with the powers of light, darkness, gods and time, its color becomes crystal blue and the front blade is extended to form a true blade, in addition to the front design forming a complete gear and extending into a sort of crossguard. Crystal blue chains additionally wrap around Trunks' arm to secure his grip. In this state, the Key Sword is powerful enough to seal Mechikabura's Time Power Unleashed form, and in the game it is additionally used to seal his youth.
- Key Sword Breaker (キーソードブレイカー) - The Super Attack of Super Saiyan God Xeno Trunks with the fully charged Key Sword in Dragon Ball Heroes.
Video Game Appearances
The Key Swords appear as items during the missions of the Dark Demon Realm Saga in Dragon Ball Heroes, where they are used by the Time Patrol to seal the Hell Gates opened by Towa in the Hell Gate Assault Saga. The player starts each battle in that saga in possession of a Key Sword, and at the end of their attack phase can attack the enemy using the Key Sword. If the player wins the Charge Impact, the enemy is pierced by the Key Sword, which causes damage, halves their Guard and increases their Charge Impact speed. The Key Sword can be stolen from the person holding it if they lose a Charge Impact while defending. Winning a battle while holding a Key Sword will award the player with a Dragon Ball.
The Key Swords later reappear as items during the missions of the Dark King Mechikabura Saga, where each member of the Time Patrol-Demigra Army alliance is given one by Demigra to close the Hell Gates protecting Mechikabura's Tower.
Xeno Trunks uses his fully-charged Key Sword first to seal Mechikabura's Time Power Unleashed form, giving Xeno Vegito the opportunity to hit him hard enough to revert him to his base form. Xeno Trunks then seals Mechikabura's youth, further weakening him enough for Chronoa to seal him away in the Labyrinth of Light.
- Its name and design is likely a reference to the Keyblade in the Kingdom Hearts franchise.