Izzan Berry Extract

The dark berries of the Izzan bush, though beloved by birds, are generally of little interest to most people. The berries stain only briefly, and thus make a poor dye. The berries are not sweet, and in fact have little flavor at all, and often make the consumer nauseous, so they have no value as food. So what value is there in the Izzan berry?
When the berries are mashed, and stirred with woodash, the pulp separates. The top layer is dark grey and thick, and contains the bulk of the ash. There is no known use for this byproduct apart from compost, and it is so discarded. What lies beneath is a thin, deeply purple liquid. This is Izzan Berry Extract.
Izzan Berry Extract is a caustic compound to most animals as well as humans. Contact with the skin will cause mild irritation, but not a severe reaction. Open wounds, however, will inflame and often widen, accelerating damage and causing a painful burning sensation. While not usually enough to kill, these reactions can weaken opponents enough that their guard can be overcome with a lethal blow. As such, Izzan Berry Extract is a popular battlefield poison.
There are two main methods of application of the extract. The most common is to soak a rag in the extract and to wipe it across the cutting blade of one's chosen weapon, be it a sword or the tips of an arrow. Some enterprising souls will occasionally wipe the head of a hammer in the stuff, and the blunt force trauma can in fact produce a gash for the extract to effect, however this is broadly ineffective. The second method of application can only be done at the time of a weapons creation. At the time of tempering, Izzan Berry Extract can be added to the cooling oil. While this does ensure that each strike of the weapon will carry the sting of the poison, the weapons themselves suffer in quality, leaving a softer cutting edge.