Thyssel bark was a type of tree bark found only on Haruun Kal, harvested from a thyssel tree. It was very expensive during the time of the Clone Wars due to the fact that, when chewed, it had hallucinogenic properties similar to those of spice. When chewed raw, it was strong enough to permanently alter brain chemistry; when refined through roasting, it was no more harmful than mild wine.
When chewed, it gave the user red-stained teeth. The thyssel bark trade funded the Balawai government of the planet. It was eaten by grassers, which caused friction between the Balawai, who wanted to harvest the thyssel bark, and the Korunnai, who wanted it for their grassers.