Note that this does not exist in Minecraft; it was written purely as a fiction article.City Creepers are a common mob spawned around player-made houses or buildings. They remain passive unless provoked. They can blend in with their surroundings. When attacked, City Creepers will revert to their origonal city pattern (as if toggling off the camouflage) and charge at whoever attacked it.
When agravated, City Creepers will simply ram into their target and explode when under low health. The explosion deals half the damage of a normal creeper's explosion, but the crater left behind is 4x bigger, which can deal a huge amount of structial damage. It is powerful enough to break Cobblestone and when in a huge group, yes, possible two or three Obsidian blocks.
City Creepers tend to cluster together near player-made structures, like houses. The thing to watch out for is moving black triangles. These mark out their feet. A distorted aura will surround City Creepers under camouflage.