Invasion of The Nether

Sudden Nether Portals appear, pouring from them, piglins, hoglins, skeletons, endermen, blazes, wither skeletons, etc. They all suddenly invade your fortress and builds, similar to the Pillagers. Maybe they even make small outposts you must destroy. Either way, another thing for the player to fend against as random events. Could be a later game event, as they drop few netherite and armor trims, and maybe wither skulls to easier access the Wither.