I am trying to spawn my custom entity in a nether fortresses.

What I tried so far is using the WorldEvent.PotentialSpawns event, but that did not really work out

My code so far

	@SubscribeEvent
	public void onFeatureRegistry(final WorldEvent.PotentialSpawns event) {
		if (event.getType() == EntityClassification.MONSTER) {

			boolean isFortress = ((ServerWorld) event.getWorld()).structureFeatureManager()
					.getStructureAt(event.getPos(), true, Structure.NETHER_BRIDGE).isValid();

			boolean isNetherBrick = event.getWorld().getBlockState(event.getPos().below())
					.getBlock() == Blocks.NETHER_BRICKS;

			if (isFortress && isNetherBrick) {

				Main.LOGGER.info("ADDED " + event.getPos().toShortString());

				event.getList().add(new Spawners(ModEntityTypes.NETHER_KNIGHT_ENTITY.get(), 50, 5, 5));
			}
		}
	}

the conditions are definitely met, because my log message is triggered when I am near a fortress, but my mob does not spawn.

Even with a higher item weight for the Spawners it does not work.

use StructureSpawnListGatherEvent and not WorldEvent.PotentialSpawns

Thank you very much, works perfectly now