Pelts

Pelts can be earned from doing tasks for Trevor The Trapper (and 4 are given from the Shepherd's quest). They can then be spent for upgrading farming minions from tier 11 (XI) to tier 12 (XII) by Terry's Shop in the Trappers Den using 75 pelts, plus some assorted items (see here). Similarly to Mithril Powder, pelts are not physical items. You can see how many pelts you have in the tablist.