Warp wood oil

A flask thrown at wood, which turns whatever it lands on into a swollen and gnarled mess. The wood is not killed by it. It writhes, thickens and goes wrong, and it does so along the grain, so a man who can read grain can say in advance where the warping will travel and, more usefully, where it will not.

Mikhail bought one for thirty gold in the downtime week and carried it north unspent, then handed it to Koa at the Twisted Grove. Koa threw it at the death-tree, read the grain while the trunk was still moving, and forced a barrel of oil into the churn until the wood had closed three-quarters of the way around it and held it there.