Simple Incense is the building material for the church’s first censer, Church Smells I, which takes 3. At the Formulation Bench, a Melted Fat and a Fragrance make one, with a 60% chance of a second from the Alchemist perk. The recipe and the censer come with the Church Smells I technology (10 red, 50 green, 30 blue).
The town Apothecary sells 10 at every tier; the Trademaster at the port also has 10, with 3 silver added to each.