There will be a 10% chance of an obsidian end pillar having a dungeon under it.
The dungeon will have a new mob named Oxfish and will be the obsidian version of a silverfish, it will have the same damage as enderman and will be immortal to all types of attacks until the enderdragon is defeated. (The power of the enderdragon keeps them immortal.) The dungeon will have black redstone ores that drop black redstone power when mined with a diamond pickaxe. The ores will spawn Oxfish when you mine them so be careful.
The dungeon will be small but it will have dispenser and tripwire traps.
Will have the same blast resistance as obsidian and it can be pushed and pulled by a piston. (It will not drop if the block under it is pushed or pulled and will be pulled along with the block.) It cannot be crafted into anything. It can be powered by normal redstone, redstone torches and can be connected to repeaters etc...
The Black Silverfish Only Spawn Inside The Dungeon, Not On The Surface Of The End
Even if they are invulnerable to our attacks, who would leave the surface of The End in the middle of an Ender Dragon fight that can noclip through the ground and into any block just to see this tiny, cramped structure to get beaten down by redundant versions of silverfish or traps. This structure doesn't exactly make the slightest bit sense. And I don't even think there's a reward in the end of it all, so why go down there or approach it? The Black Redstone won't even be good for anything other than aesthetic and doesn't even include other variations of it.