Pictured is the Death Star II's reactor core.
A main reactor, also referenced as a reactor core or simply a reactor, served as a primary device for generating power, commonly implemented within space stations and various spacecraft. Reactors, including chemical, fission, and nuclear fusion types, have been in use as far back as the early era of the Republic. Frequently, these reactors necessitated the acquisition of diverse fuel sources from local areas. In contrast, larger starships often relied on hypermatter annihilation reactors to produce significant quantities of energy. Nevertheless, many fuel types presented hazards to living creatures, circulating through ship systems either as corrosive fluids or as flammable and poisonous gases.
Both the Death Star and its successor, the DS-2 Death Star II Mobile Battle Station, which were planet-destroying space stations constructed by the Galactic Empire, contained reactor cores. Should these cores be struck by sufficiently powerful weaponry, they would detonate, resulting in the destruction of the entire station.
The Xyston-class Star Destroyers' axial superlaser also possessed the capability to disintegrate planets. Such immense power demanded a direct link to the Star Destroyer's solar ionization reactor. Consequently, critical damage inflicted upon the superlaser would initiate a cascade effect, overwhelming the host ship's reactor core and triggering the warship's demise.