How to Obtain and Use Must
Getting Must
Must is one of the mod's blocks and is produced through its crafting recipes. Check your recipe book for the shaped or shapeless recipe that outputs Must, gather the listed ingredients, and craft it at a crafting table. Must is a block, so once crafted you can place it in the world like any other block.
Where Must Fits
Must is a distinct block from Bacterium — it is not the same material and does not behave as the infection does. Treat it as its own resource: craft it, place it, and use it as an ingredient or building block in the mod's progression.
Working Alongside the Other Tools
If you are managing a Bacterium problem, Must is a separate concern from the Bacterium Jammer, Bacterium Replacer, and Bacterium Splash Potion. Those three handle stopping, converting, and spreading Bacterium. Must is crafted and placed on its own track.
Keep a stock of Must if a recipe you are following calls for it, since it is a crafted block rather than something you find. Produce it in batches at the crafting table so you are not stopping mid-build to craft one at a time. Store it with your other mod blocks so it is easy to find when a recipe needs it.