Playing on my server, when an undead army event happens mob spawners are placed in the air. Typically where the player started the event. The spawners don't disappear after the event as well. It also appears that during an undead event where the spawner is, is where the army runs to.

The server is on 1.16.4. Everyone's client is Forge 35.1.37. Mod version: 0.4.0
If you need any additional info, let me know. Thanks for the mod! Me and my friends are having a lot of fun with it!

Thanks it has been fixed and will work correctly in the next update.