When I tried to attach a Greater Focus to my 'new' Void gauntlet the game instantly crashed, since then I can't even rejoin the server as "The game crashed whilst unexpected error
Error: java.lang.ClassCastException: thaumcraft.api.casters.FocusPackage cannot be cast to thaumcraft.api.items.IArchitect" error repeatedly crashes the game
crash-2019-05-02_22.11.07-client.txt

You appear to be running an old version (1.0.3), this was fixed in the version after yours (>= 1.0.4). Updating will stop the crashes.

Closing as duplicate of #4.