Nether reactor cores could be used to create Nether reactors, which would transport the player into a tower made of netherrack known as the Nether Spire. Nether reactor cores no longer have a function due to the addition of the Nether. Nether reactor cores now drop 6 iron ingots and 3 diamonds.
Ah yes nether reactor core, used to create nether reactor, which was a player-built structure exclusive to Bedrock Edition which, when activated, spawned large quantities of normally rare or unobtainable items.