more nether reactor cores?

[obtuse timber]

well in the datapack Incendium by Stardust labs, there is a structure called the nether reactor. this is a datapack so 100% not canon but i like to think of it as the core used to be in the center but was removed. the reactors themselves are run down and such.

[eternal prism]

There is an argument to be made that nether portals do kind of act like nether reactors, considering that they are oftem shown to bring the nether into the overworld

(see also ruined portals and mcl)