The war mask is a tribal clothing item. It provides minor protection, as well as increases pain threshold, allowing its wearer to take more damage before crumpling.
It can only be made by tribal factions. It is crafted using 50 wood at a crafting spot, and costs 5,000 (83.33 secs) worth of work to finish.
It is a cheap way to armor up your tribespeople in the early game, if you have a good craftsman. While it doesn't give much protection, the increase in pain shock threshold helps your tribespeople stay longer in the fight before giving in to pain.
Wood is reasonably easy to obtain in most biomes, so obtaining materials shouldn't be too much of an issue. Rather, the greater issue is having to divert labor to obtaining the wood and crafting it.
The following table lists how much protection a war mask provides at each quality level.