The Time Blades are four blades from the Ninjago theme, specifically the season seven story arc Hands of Time and its associated toys; as their name implies, they are four blades that each have a different power over the element of time.
The powers of the Time Blades originally belonged to Acronix and Krux, the Elemental Masters of Time who turned against their comrades. In order to defeat them, the other Elemental Masters had the blades forged by Ray and Maya from Chronosteel, a unique metal with the ability to absorb Elemental energy to the point of removing the powers of an Elemental Master. Wu and Garmadon then wielded these blades in battle against the Hands of Time and were able to drain their powers, with each blade gaining a different ability. Wu and Garmadon then used the blades to open a vortex so as to scatter the Time Blades across the ages, as it was felt that no one should possess power over Time again. The blades were then hurled into the vortex but pursued by Acronix and Krux; Acronix ended up being sent forward forty years into the future, while Krux vanished but somehow managed to return and live in Ninjago under the assumed identity of Dr. Saunders.
The green Fast Forward Time Blade possessed the ability to cause Time to move forward more quickly. It returned to Ninjago shortly after Acronix did, and unleashed a wave of energy that skipped time forward one minute; Acronix then seized the blade and used it to continue his battle with Wu. After using it to defeat Wu with his "Time Punch", which caused Wu's aging process to begin accelerating rapidly, he employed it in a brief battle with the Ninja before using it to escape, creating the illusion of his own demise in the process. Acronix would subsequently use the blade to ambush Zane in order to kidnap Cyrus Borg and to effect his and Krux's escape from Kai and Nya with Borg in tow. It was briefly taken from Acronix by Lloyd but reclaimed by General Machia; Acronix would later use it to strike Ray with a Time Punch as well before placing it in the Iron Doom.
The blue Slow-Mo Time Blade has the power to make Time move more slowly. It emerged from the vortex some time after Acronix and Krux unleashed their Vermillion army upon Ninjago, and the Hands of Time quickly directed their forces to recover it. They succeeded, but soon lost the blade to the ninja due to the efforts of Jay, only to recover it during their attack on the Temple of Airjitzu. After using it a number of times in battle, the Time Twins would place it in the Iron Doom with the other blades, enabling them to use the machine to travel through time.
The red Pause Time Blade has the ability to freeze Time, and was the last blade to return to Ninjago. Acronix and Krux homed in on its arrival point using Acronix's BorgWatch, which possessed a temporal scanner; their success made Borg regret adding that feature. They would subsequently use it against Ray and then against his family and Wu, the latter occasion preceding them leaving the five to fall into the Boiling Sea. Acronix and Krux also used it to stop Cyrus Borg, Samurai X, and Zane from causing the Iron Doom to self-destruct, before placing the blade within the mech so as to travel back in time. It would later be lost along with the Fast Forward and Slow-Mo Time Blades when the Iron Doom was cast adrift in time with Acronix, Krux, the Vermillion snakes, and Wu aboard.
The orange Reversal Time Blade has the ability to cause Time to move backwards. It was the first blade to return to Ninjago, emerging unnoticed with Krux from the Temporal Vortex, and was found by Ray and Maya and hidden in the library of Hono Mizu in the Boiling Sea. However, the Time Twins later forced Kai and Nya to retrieve it, as it was the only means by which they could reverse Wu's aging process and save his life; later it would also become essential to saving Ray as well. Having been added to the Iron Doom, it completed the mech's power to travel through time, but attempts to remove it initially proved fruitless. Fortunately, their presence in the past allowed Nya to make use of the past Reversal Blade-which hadn't yet been hidden-to heal Wu and enable the present heroes to pursue the Time Twins, leaving the blade with the younger Wu to preserve history. The old Wu would then succeed in removing the blade from Iron Doom and gave it to Kai and Nya to heal their father; after they did so, Lloyd determined that the ninja would dispose of the blade.