Drumanone Offering Altar is found northeast of Rathcroghan.
Offer 5 Deer Hooves to Drumanone Offering Altar
This offering altar requires that you offer 5 Deer Hooves. If you’ve been doing any form of light hunting in this game, chances are you already have some hooves in your inventory, however, if you don’t you’ll be able to find some deer around 350m south of the offering altar. If you’re having trouble tracking down some deer in the vicinity you can use Odin’s Sight or even send up your raven to scout out the area!