Now we getting to some grade A, primo material with A1: Slave Pits of the Undercity. I first played this module right when I was getting into AD&D and lots of it is permanently burnt into my memory chips. Fighting the aspis, the sundew that smart players threw vinegar on [I am looking at you Jerry Snyder], the early ghoul encounter that went extremely poorly, another orc witch doctor, two basilisks, the 5th-level thief with invisibility who is looking to backstab, this adventure had it all.
But the one that mattered most was fighting the giant grub-cow in the aspis breeding pits. This beast had 60 hit points, which is a lot, lot, lot when Kirwin the Mentalist has 12 as a 4th-level magic user, and Dingorn the Stalwart has a longsword that does 1d10 damage. The cow also exudes a “milky acidic slime” that can cause damage if touched, as well as eating through metal. Upside of killing the cow: a bunch of experience points, and, rarity of rarity, platinum pieces. A full one hundred of them.