I'm not entirely sure why, but Black Powder seems to be incompatible with Fabric 1.17.1 BCLib, from version 0.4.2 to 0.5.5. Found this issue while trying to add Black Powder to a modpack I'm building, systematically removed and readded mods until I found the conflict. Log of attempting to run Black Powder 1.0.6 with BCLib 0.5.5 attached.
latest.log

Yea this is another Multi-Item-Lib issue, This won't be fixed till the overhaul which is a long while off sorry.

And it'll only be for 1.18 when I do make it.

Alright, thank you.