How the blocks were arranged to make a nether reactor.
The reactor was constructed by placing gold blocks, cobblestone, and a nether reactor core in the 3×3×3 arrangement shown to the right. Air blocks were required on the middle and top layers.
If the structure was incorrect, attempting to activate the reactor resulted in the client message "Not the correct pattern!".
Client message: Active!
Client message: Not the correct pattern!
Cannot activate due to an incorrect structure pattern.
Client message: All players need to be close to the reactor.
All players must be close to the reactor to be activated.
Client message: The nether reactor needs to be built lower down.
Nether spire cannot be created because the location of the nether reactor is too high.
To active a nether reactor, the following conditions needed to be met:
All players were in the range of the reactor's effects on activation.
The reactor was built within the valid range (Y: 4–96).
The player who activated the reactor was standing level with the structure.
If those conditions were met, tapping the core would activate the reactor, sending the client message "Active!". Immediately after activation, a massive structure of netherrack with multiple rooms, referred to as a Nether spire, was generated around the reactor. The bottom room, which contains the reactor, replaced all blocks other than those of the reactor with air, while blocks in the upper levels remained intact.
The reactor cycle would end after 45 seconds, damaging the reactor's structure and changing the world to night.
The reactor was replaced with a 3×3×3 box of obsidian containing the core, which adopted a darker, blue-black texture to indicate that the reaction has ended. If the player built a new reactor around the burnt-out core, the netherrack spire would generate, although the rest of the reaction would not take place.
The nether reactor's functionality has been removed with the addition of the Nether. While the nether reactor blocks still exist, they serve no purpose.
The spire was composed of over 25 stacks worth of netherrack.
Excluding the core, any part of the reactor could be mined after activation and it would still function. This way, the player could recycle the expensive gold blocks. It was possible to recover all 4 blocks provided the player worked quickly.
Because the spire could not replace blocks past the world border, when the reactor was activated near the edge of old worlds the player would be able to see the time set to night.
If the nether reactor core was mined out while the nether reactor is active, the glowing obsidian would not turn into obsidian after the reactor deactivates. This also caused the reactor to stop spawning items and zombie pigmen, and make the day/night cycle freeze at nighttime for several in-game days.