This article is about a/an group of villains in Hyakujuu Sentai Gaoranger.
The Thousand-Year Evil (千年邪鬼 Sennen Jakii 27-31) is a malignant mass of energy born from the original Org invasion 1,000 years ago that was contained within a wolf mask known as the Dark Mask. In the past, Shirogane harnessed the power of the mask to combine his three Power Animals into GaoHunter and thus be able to kill Ultimate Org Hyakkimaru. However, even though he managed to finish off the Org, the evil spirit took full control of Shirogane's body which ended up transforming him into the Duke Org Rouki, while transforming GaoHunter into GaoHunter Evil, and its Power Animals into Demon Beasts in the process. Unable to control its power, Shirogane had his allies seal him in a stone coffin to avoid harming anyone.

Centuries later, Rouki was released by the Highness Duke Org Ura to fight against the Gaorangers, remembering only his millennium-long imprisonment by the original Gao heroes. Over time, Rouki began to remember who he was, but Ura implanted a special grasshopper in him to modify his memory and turn him into his obedient servant. Rouki was then defeated by the Gaorangers, who managed to defeat GaoHunter Evil to break the curse, freeing both Shirogane and his Power Animals from the malign power in the process. Later, the Thousand-Year Evil used the mask to return as Rouki, with the intention of killing Shirogane for using his power. In the end, Rouki was finally defeated by the combined efforts of GaoSilver and Gaorangers, and killed by GaoHunter Justice. Although the mask was destroyed, the Thousand-Year Evil survived. Ura would use it to create powerful Orgs to fight the Gaorangers, while giving to the Duchess Org TsueTsue and Duke Org Yabaiba residual energy to change their appearances and transform them into their Armored Forms and increase their powers.

With each Org created with the evil energy that was defeated, the Thousand-Year Evil's grudge matured, causing it to increase in power. Eventually, after the Gaorangers defeated Tombstone Org with GaoMuscle, they used the newly formed GaoKing Cross Horn to imprison the spirit so it could not be used to make anymore Orgs. Despite being sealed, however, the spirit was still out there.

Ura then captured Shirogane, intent on making him reabsorb the evil power to turn back into Rouki. Using Shirogane's weapon, Ura broke the seal on the Thousand-Year Evil and allowed it to reenter Shirogane's body. While it at first looked like it had overwhelmed him, Shirogane managed to reject the spirit, finally severing his millennium-long bond to it. However, this was actually what Ura wanted, enabling him to use his mirror to absorb the Thousand-Year Evil and evolve into a more powerful form, which he reveals was his plan from the very beginning, and also revealing the reason why he freed Shirogane from his imprisonment and then cultivated the evil power in the Orgs. With the power of the Thousand-Year Evil inside him, Ura massacred the Gaoranger, leaving Kakeru and Shirogane as the sole survivors. While the two tried to fight the strengthened Ura on their own, in the hereafter, the four dead Gaorangers provide GaoRed with the Falcon Summoner, allowing him to kill Ura with a single shot, though he instantly resurrected into a giant. GaoRed then received the jewel of GaoFalcon while GaoGod revived the other Gaorangers to help form GaoIcarus. After an aerial battle, Ura was purged of the Thousand-Year Evil after being wounded by the Icarus Dynamite, returning him to his original form. Weakened, Ura was wounded by GaoSilver and finally killed by the Gaoranger's Hyakuujuuken, destroying the Thousand-Year Evil forever, while Tsuetsue and Yabaiba returned to their original forms as a result.

Thousand-Year Evil Users

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