This mod is incompatible with Gunpowder-MC(with utilities extension) or the latest Fabric API at point of writing.
I used this mod perfectly before adding Gunpowder and the latest Fabric API.
This is the issue we were talking about on Discord, only now I found out the conflicting mods.
Would it be possible for you to add support or should I just remove gunpowder?(Your mod is better so I would remove Gunpowder if I had to remove one)

No, I'd love to make it not conflict with Gunpowder ...
The problem is that I'm kinda stuck with releases if Taterzens were really the one to cause the corruptions ...

wait: or did I understand it wrong and Gunpowder + Taterzens is the corruption combo?

Yes Gunpowder+Taterzens is the "corruption combo".
Or Taterzens and the latest Fabric API
I'd been using Taterzens(0.2.0) before I added Gunpowder + Gunpowder Utilities perfectly fine. It was only after I added Gunpowder and updated the Fabric API that Taterzens stopped me joining. I can tell it was Taterzens because it was the /npc create command. The other commands were fine.

I am unable to actually test it, due to the unfortunate issue of not being able to access Minecraft for a few months minimum.

I've checked this more and reported issue in Gunpowder, Gunpowder-MC/GunpowderUtilities#17
as the fault is missing null check.

So I just have to wait until Gunpowder fix this.
If they even will as the last thing on their repo was on the 17th January

This has been fixed in gunpowder :)