Past Millstones gave you conversion rates similar to a Granite Shard kill
Kor Haven and Glacial Chasm are other ways to do this, and while they are strong cards, I would caution against overly committing to a pillowfort
1 Rare or mythic rare, including Booster Fun, double-faced, and retro frame cards Here you can get any of the 60 MH3 rares (79.8%) or 20 mythic rares, including DFC planeswalkers (13.0%), retro frame cards (24 rares, 8 mythic rares [2.1% in total]), or a Booster Fun borderless card, including fetch lands, concept Eldrazi, DFC planeswalkers, frame break cards, profile cards, and other borderless rares or mythic rares (5.1% in total)
Legendary Creature - Bat God Bandit's Talent (Gain the next level as a sorcery to add its ability.) When this Class enters, each opponent discards two cards unless they discard a nonland card
Manipulating the Lore Counters on Saga cards is a novel way to run this card too
How Much Mana Do You Need for a Goblin Deck