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Power Blade and Power Blade 2 were action platform releases exlusive to the NES. Powerblade was released in 1991 and quickly followed by a sequel in 1992. The plots for each of these games follows - please see the VGG game entries for details.
Plot for Power Blade
After years of fighting that took millions of casualties, Earth was recovering from revolts in the 22nd century. In 2191, New Earth has a Master Computer that holds a secret database of the colony-planet's functioning. In wrong hands, the database could prove fatal to the whole planet. One day, aliens attack the Master Computer, making the Master control program malfunction. Nova, a lord of the ancient Power Blade is summoned to take care of the situation. The Power Blade is a glowing energy boomerang that Nova uses to defend himself.
In order to access the Master Computer's Control Center, Nova first has to obtain tape units from the six sectors surrounding the Master Computer. Each sector is heavily guarded by aliens, and Nova has to locate and contact an agent first to receive an ID card used to access the security room located at the same sector. After defeating the security room guards, Nova can obtain the sector's tape unit and use it to disarm the sector. After the six sectors have been disarmed, Nova must fight his way through the Control Center, destroy the Master Computer and restore order to the society.
Plot for Power Blade 2
The game takes place in the year 2200 and follows NOVA the protagonist from the first Power Blade game as he sets out on a mission from the U.S. Department of Defense to destroy the Delta Foundation, who has created a new cyborg that can threaten global security if it falls into the wrong hands. Just as in Power Blade, this game is similar in gameplay to the Mega Man series in that the player has the freedom to select any stage to play. It also adds some new features also seen in the Mega Man series, such as the ability of the player to slide and a wide assortment of weaponry.
Source: Wikipedia, "Power_Blade", available under the CC-BY-SA License.