The Arcane Blade (Thaumcraft version of the sacrificial knife) does not work properly as I doesnt actually drain your life but just makes it look like as if the hearts are missing. The Altar doesnt get any LP aswell. If you look at the page of the Arcane Blade in the Thaumonomicon for too long it crashes your client. Same happens when you try to shift click the blade in your inventory.
Issue was fixed in V0.8.2 of the mod but the modpack doesnt have the updated version. @MaelstromPhoenix will need to update the pack
@MaelstromPhoenix , could you please update the pack, I would really like to use that mod and it doesnt seem like a big thing to do. Also having a crashing item ingame isn't exactly good