As an action, you can create this flammable oil. As an action, a creature can coat one weapon with the oil to cause it to ignite in flames. For the duration, the weapon deals an extra 1d6 fire damage when it hits.
Alternatively, you can touch a quiver containing arrows or bolts, granting the ammunition pulled from it the same effect. The oil’s effect ends on a piece of ammunition when it hits or misses.
You can increase the damage by 1d6 for each additional catalyst expended