For the best chances at finding those elusive shards youll want to focus on the skull cavern, especially going deep with plenty of bombs and staircases. The iridium nodes start showing up more frequently past level 100, and they have about a 4% chance to drop one which isnt bad at all. Keep an eye out for those mystic stones too, since they have a solid 25% chance and can spawn in both the cavern and quarry.

Something interesting about the daily grind is setting up a rainbow trout pond with 9 fish, gives you a tiny shot each morning at getting one. While youre waiting on that, breaking omni geodes from krobus on tuesdays is worth trying, and the burglar ring helps a ton when farming monsters since it doubles your chances for drops. The timing on ring usage is pretty crucial, especially against serpents and mummies which have slightly better drop rates than regular enemies.

For guaranteed success, the summit chest in the volcano dungeon contains one on your first clear, just make sure to position yourself carefully around the lava pools. The most efficient approach is definitely combining methods - running skull cavern with lucky lunch active, checking the quarry daily for mystic stones, and keeping that fish pond going while you focus on other activities. Just remember that deeper cavern levels mean better odds, so save those staircases for quick depth gains when you're hunting specifically for shards.