Single-Use, Consumable Magical Wonders have always been some of my favorites, especially when they present the Players with incredibly specific solutions to hereto unknown problems. There’s an immense sense of satisfaction when you happen to have just the right tool for the job, or the final piece that helps a plan or scheme succeed.
As I was thinking about these sorts of things, I decided to do a Table of Incense or Candles. These items may be burnt (and consumed) to produce a special effect but are generally temporary in nature: lasting only as long as the Candle burns, or the incense remains fragrant. Requiring a source of Fire, and hampered by damp or windy conditions, activating these can sometimes be a challenge in itself. I imagine the radius or duration of effect might be rather limited as well in most cases.
Here are a hundred ideas for adding these kinds of flammable wonders to those Treasure Hoards. Potentially those with specific knowledge could even manufacture these (via Magical Research, or perhaps by acquiring special Reagents), or the less spectacular/more utilitarian entries could even be found for sale or barter by specific Vendors (Incense Mongers in my games always only accept Electrum).