At some point this mysterious person acquired Nya's old Samurai Armor and recreated it into his/her armor.
The Battle of The Temple of the Airjitzu Master
This mysterious samurai first appeared when Lloyd was knocked off of concentration and lost control of his dragon cause of the Vermillion shells. When Lloyd lost control he appeared on his samurai suit to save him. While aiding the Ninja against The Hands Of Time and their Vermillion army, this person got shot down by the Vermillion Warriors, and then after the battle mysteriously disappeared without a trace.
Fighting the former Samurai X
Nya, who was jealous that someone stole her old armor and wanted to best the new Samurai X. She later returned to the Samurai X Cave where she found the mysterious new samurai. At first she taught he was a Vermillion but was proven wrong. As they fought Nya then vowed that the new samurai is worthy of her former armor and gave the samurai her old cave and a vehicle as she raced to her brother at Chen's Noodle House.
Tracking Cyrus Borg
It is unknown if this samurai was hired by the Borg Industries to trace and find Borg. When the Ninja's plan to rescue Borg failed, this mysterious person appeared out of nowhere on the Vehicle that Nya gave and saved them. As the samurai was about to take Borg and the Ninja away from the Vermillion Swamps, he accepted a challenge from Zane to deactivate the Iron Doom and took Borg with him to activate the self-destruct code in the apparatus. When they arrived, Zane helped Borg deactivate the Time Apparatus as The Hands Of Time and Supreme Commander Machia arrived at the swamp. However they failed to deactivate the Iron Doom because Krux used the Pause Time Blade to pause Time on Zane, Borg, and the Samurai. Following that Acronix and Krux plugged the Blades in the Time Apparatus of the Iron Doom traveled back in Time to exact their revenge.
Hoping for Victory
After the Hands of Time left along with Kai, Nya, and Wu they hoped that they will stop the Time Twins. Eventually, the Time Twins won for a while leaving Samurai X nowhere to be seen. This continued until Kai and Nya used the Past Reversal Time Blade to correct the timeline of Ninjago, allowing Samurai X to return. When Wu used the Reversal Time Blade to sabotage the Doom he tossed the Kai and Nya along with the Reversal Blade into the present Time, Kai healed his father after that the Samurai witnessed Lloyd's speech to dispose of the Blade and find Wu.