The Reactor Core is the central power source of the Flying Battleship Balrog, whose energy allows the giant airship to soar the skies. The actual core is formed by a mysterious "aquatic lifeform" known as a Merrow, a mermaid-like woman, encased upside-down in a large containment tube. This mysterious creature generates the energy used by the Balrog, a process that's painful and exhausting to the point she desires death.
All the energy the Merrow generates goes to power the Balrog, but the strength of the energy is so great that she can't control it alone. Due to this, she's surrounded by four Control Brains (制御脳) encased in smaller tubes. These Control Brains retain and manage the large output of energy the Merrow generates. If three of these brains are incapacitated, however, the piled-up energy goes completely out of control.
The Reactor Core is Hiryu's main objective to destroy during his infiltration of the airship. Once he arrives at the Central Engine Room, the anguished Merrow begs him to kill her. Hiryu faces the Reactor Core's attacks and eventually fulfils her wish, destroying the entire machine and dealing a crippling blow to the Balrog.
The Reactor Core stands in a small, circular room whose walls are in constant movement. There's a raised platform in the center of the room, with the core itself and its four Control Brains hanging directly above in the ceiling. In order to reach it, there are two yellow platforms moving in circles at both sides of the room.
The Reactor Core remains static in its place, only shooting projectiles at Hiryu. Another hazard Hiryu has to look for is an electric bolt that generates between the yellow platforms. These attacks are more recurrent when the Reactor Core has lost half of its health bar. The main difficulty in this battle lies in the core's position, which requires Hiryu to move and jump constantly in order to reach and attack as well as to avoid any upcoming projectile.
There are two item boxes at each side of the Reactor Core, holding a Cypher and Life+1 power-ups.
- Electric Pulse: The spikes atop the core generate an electric orb and shoots it at Hiryu. The orb moves slowly and homes in on Hiryu, but it can be deflected away with a single Cypher slash. If aimed correctly, it can actually be shot back at the core, damaging it slightly.
- Lightning Bolt: A bolt of lightning generates from one yellow platform, aiming at the platform closest to it. The bolts usually generate toward the platform Hiryu is stading on, traveling from an empty platform to the one Hiryu is occupying, linking both together briefly. The attack itself is harmless if Hiryu is standing in either platform, but it can become an obstacle while Hiryu is jumping around.
- Power Surge: The Reactor Core unleashes a large pilar of energy in Hiryu's position, accompanied by a chorus-like scream. A line of energy indicates when it is about to appear, giving time to evade. The attack is only used after the Core has lost half its health.
The Reactor Core went through significant design changes during development. The initial concept sketch presented the Merrow in the center of a single, thin pillar in the middle of a vast circular room with no visible floor. The Control Brains appeared inside small circular containers linked together by a belt, constantly spinning around the core, and shooting electricity at Hiryu. While there was no floor to stand on, two large rings made of square-shaped segments surrounded the core. Besides serving as footing for Hiryu, it'd also become an obstacle by separating its sections apart, which would then float around. It's presumed this design was scrapped because it'd have been unwieldy to create with the technology of the time.
The second concept sketch shows the Reactor Core in its final design, although with a few minor differences. Instead of the yellow platforms, two large rings surrounded the core diagonally, providing a way to reach it. The yellow platforms were instead on the lower walls of the room and would come out in groups of two. The platforms would be released periodically and fly around, attacking Hiryu with electric attacks. The rings were dropped and the platform's behavior was simplified in the final in-game boss battle.
Project X Zone 2
The Reactor Core makes a brief cameo appearance in Project X Zone 2 during Chapter 23. Both the Development Dock and Reactor Core appear in background artwork when the characters visit the locations to plant bombs in their attempt to destroy the Balrog. The Merrow is also referenced in an Accessory item obtained during and after this chapter, called "Scale of the Mysterious Aquatic Lifeform" ("Sea-Dweller's Scale" in English), which increases the chance of Fainting by 10%.
- Capcom (February 22, 2014). Strider Hiryu Visual Chronicle (Japanese). Pg. 43
- Capcom (December 1999, Arcade). Strider Hiryu 2 (Japanese). Stage 4 Briefing