Fortress/Bastion + Ominous Bottle: Armageddon

If you enter a bastion with the ominous effect, a bunch of nether fortress mobs attack it. Wither skeletons & zombified piglins with netherite gear (they wouldn’t drop it), masses of blazes, huge magma cubes, maybe even Ghast jockeys. They’d all fight with the residents. If you enter a nether fortress with the ominous effect, it’s attacked by piglins in gold armor, some even netherite (again, no dropping netherite), drinking fire res potions, adult hoglin jockeys, strider jockeys, Piglin brutes attacking blaze spawners, etc. Whoever is invading th other structure would spawn like a raid, and eventually either run out of waves or kill all the mobs in the defending structure. It expands the piglins vs wither skeletons hostility into old nether vs new nether, while providing a very unique event.