The Kodai insignia is obtained as a possible reward from the Chambers of Xeric. It has an Inspect option which will result in the chatbox stating, "You sense a dark magic emanating from the insignia. It looks like this could be attached to a wand." It is used on a master wand to create the kodai wand, which requires 80 Magic to wield. This process cannot be reverted.
When creating the wand, the chatbox will then state, "Power shoots down the length of the wand, empowering it with the darkness of Xeric's Kodai wizards."
For an exhaustive list of all known sources for this item, see here
- Upon release of the Chambers of Xeric, the Kodai wand itself was dropped instead of the insignia. This was an oversight, and was fixed a week after the Chambers' release.