Caoutchouc can be obtained from various plants – keep yours eyes open for the ones with green and red leaves, or red spikes. You can also get it for clearing certain trees and bushes, and opening gifts on some islands. Keep in mind that caoutchouc is rare, and will not drop from every plant or tree you chop down.
You can also get caoutchouc as a reward for fulfilling Dragôn Mysterium requests. Check out the section Merchant and Dragôn Mysterium for more useful information on other resources you can get at the Dragôn Mysterium.
Caoutchouc is useful for many things. You will need it on Spirits, Tangled, Serenilla, Star Reach, and Emerald Islands. It is also required for upgrading the Stone Poem.
To learn more about resources and where to find them, check out our Resources section.