Arcana Botanica is based in Burlington, Vermont. They produce, among other things, herbal infusion kits for cocktail bitters. We recently tried their Brimstone Bitters. Making the bitters is easy: all of the herbs come in a muslin bag which you steep in vodka for 24 hours. Far more challenging, actually, was finding a dropper bottle for dispensing. I work in a school so my first attempt was "borrowing" a dropper from one of my science teacher colleagues, though the one I tried was cracked (the dropper, not the teacher). Fortunately, one of our local grocery chains has an extensive apothecary section - bingo!
First, we tried the bitters in an Old Fashioned per the producer's suggestion. We did a taste test between the Brimstone and our usual Regan's Orange. No preference. The Brimstone definitely brings some spice to the party which was interesting. But the Regan's is cheaper so, advantage Orange.
Trying the bitters on its own (with gin) was a bit of an adventure. Truthfully, I had to water it down quite a lot before it was even drinkable. So spicy! Big picture, that makes the Brimstone a good find. I've had several bitters which were a little disappointing in terms of heat delivered - the Aztec Chocolate and the Spiced Cherry come to mind. The Brimstone would combine nicely with those, I think.