For the quest Warding Vampires I tried farming shaman garlic from Orcish Cursemakers in Yughott Grotto. After not having any luck a lvl 75 THF named Sheldon helped me. We killed dozens. Shaman Garlics drop rate is 14.1%. Black Slacks and White Mitts have a 0.3% drop rate. We got multiple drops of black slacks and white mitts but no garlic. According to those drop rates we could have expected to have got multiple garlics before we got a single black slack or white mitt.

I don't think the item drops in the game.

Sheldon Informed me that the Item ID is 1018