here is a modrinth pack with my exact setup to reproduce the issue. when you attempt to create a world paxi loads the datapack, then it crashes before getting to the create world screen. i am encountering this issue with multiple seemingly random datapacks (it is not pack format dependent), this is only one of them that has this behavior. paxi is only included to quickly test the issue, if you manually add the datapack through the vanilla method it will prevent the datapack from loading rather than crashing. i have checked to confirm that this does not happen without hordes.

nevermind, it seems the datapack actually had corrupted, not sure how that happened but it isnt the mods fault.