When I did it I "farmed" enthir about 10 times, which is 20 in game days, and Then I would go back and visit the shrine, however the shrine resets every in game week ( just looked it up lol) so you can farm enthir, then after the 4th buy, go to the shrine, then go back to him...you can accumulate alot of them really quickly, lol, OH, and I may be mixed up on which hall he's in, of he's not in countenance then he's obviously in attainment, either way he's the first room on the left at the top of the stairs lol I DO remember that much lol