Varying in its colour, Alchemic Powder is the most useful stuff in all of alchemy. It is literally what alchemy looks like. If you want to make a portal, dust a spot with alchemic powder, and it will open a portal. It will work if you have alchemic training, and strength.
Alchemists are the only ones who can use alchemic powder. But they use it. A LOT. Many don't even have it physically, and they can just will things to happen, since they're so accustomed to it at this point. Mandy is among the strongest users, and she still uses it, but carries it around spiritually, like her granddaughters, making her extremely powerful.