The 'first fruits' of the harvest. More accurately, it is donations made to a Weyr by the Holds and Halls in its territory, to support the Weyr so that the dragonriders can concentrate on fighting Thread and caring for their dragons, instead of having to work at other jobs to support themselves. Tithes consist of food, leather goods, healers' services, fabrics, and anything else needed to run a settlement of dragonriders.