Ogre Tannin

Ogre Tannin gives the Gordok Ogre Suit its color and is used to complete a Dire Maul tribute run in Dire Maul North.

Source
After you trap Guard Slip'kik in ice, climb a ramp to proceed to the next area. On the first balcony you will see an Ogre Tannin Basket on the left side in the back of the room. This basket contains the Tannin.

Note
As soon as you grab the Tannin, a Gordok Bushwacker will appear and start attacking you, so be prepared.

When a player picks up the Tannin, an ogre will say: "It puts the tannin in the basket or it gets the mallet again!" which is a reference to the movie Silence of the Lambs.

Alternate source
If you find a Gordok Shackle Key you can do the repeatable quest and set Knot Thimblejack free. There is a chance that one or two ogre Tannin will be in the crate that appears.

Use
Ogre Tannin is required to make the Gordok Ogre Suit, the reward from the quest. A leatherworker or tailor can learn to make the suit on their own by completing the quest once.