Nether Reactor Core back!

The block is still in the game but is disabled, they even bothered to change its texture! You should activate it exclusively for the ancient world with some changes, for example depending on the difficulty spawning different mobs.
Easy: 3 zombified piglin
Medium: 2 piglin and 1 skeleton
Hard: 2 piglin, 1 or 2 (50/50) skeleton and 1 wither skeleton (with 100% chance of dropping his head)

Certainly the Nether Spire, a structure that is generated when activating the nucleus had 2 or 3 floors, in the case of difficult difficulty on the first floor there can be the 3 zombified pigling and in the second the 1 pigling 1 or 2 (50/50) skeleton 1 wither skeleton and if you want to add more difficulty 1 ghast outside the structure (30% probability)

In addition to the generation of 2 books enchanted books of the same type: 20% Mending I, 30% Power III 30% Sharp III, 10% Protection III and 10% Fortune III. Since the world is very limited in resources. And with regard to the items and nether blocks, only soul arena for the other items that are generated as before.

While in the infinite world it can be found in the remains of archeology.