You are talking about ol' Urky. Can't tame named monsters, unfortunately. If you ommel fluids off orc leaders I recommend bear traps or lightning.
Beyond 10 there's no guarantee that an enchant scroll will work. I doubt you'll get 16. Save 'em for better equipment. Helmets, gloves and boots that give stats, cloaks of fire/lightning resistance, for instance, as they give you more than just AV.