Sigma Head

Sigma Head (シグマヘッド) is the boss from the Opening Stage in Mega Man X5. He wounds the character opposite to the one the player chooses (he will destroy X's Fourth Armor if the player chose Zero, or destroys Zero's buster if the player chooses X) and then hides inside a statue under construction.

History
A few months after the Great Repliforce War, Sigma hatched up a new plot to decimate humanity and create more Mavericks by spreading the Sigma Virus all over the planet. To achieve this end, he has the bounty hunter Dynamo blow a hole in the colony of Eurasia and send it on a collision course toward Earth. Meanwhile, Sigma ambushes the Maverick Hunters at a city in northern Brazil in the form of a giant head.

Although X and Zero manage to defeat Sigma in this form and cause it to explode, they did not realize until it was too late that Sigma lost to them on purpose. The explosion caused by his defeat causes the virus to spread from South America all over the Earth to different continents, resulting in the majority of Hunters becoming Mavericks themselves. Even seaside Reploids such as Tidal Whale were infected by the virus.

Strategy
In this giant head form, Sigma releases small energy spheres from his mouth or his eyes. They will be a barrage of blue spheres if he releases them from his mouth, and two green spheres that track the opponent if released from his eyes. He can also attack by ramming toward his opponent, with his reach ending at the opponent's side of the arena. After losing half of his energy, he will fire a large purple energy beam from his mouth. His only vulnerable area is the cannon's lens that only appears when he opens his mouth to attack.

Other Media
The Sigma Head appears in the Rockman X5 manhua serving the same role as in the game, only fighting both X and Zero.