Blood Moon is devastating here since Eldrazi Temple, Ugin's Labyrinth, and Urza's Saga all become plain Mountains, crippling their colorless mana engine. Their Mountains can only make red mana, so colorless costs like Devourer of Destiny, Thought-Knot Seer, and Kozilek's Command get very hard to pay. It also turns our own nonbasic lands into Mountains, so sequence it with care. Vexing Bauble stays in the sideboard: it only counters spells cast with no mana spent, and their deck has no zero-mana spells to hit. It would counter our own zero-cost artifacts like Mox Opal, Mishra's Bauble, and Tormod's Crypt. Hurkyl's Recall gives some tempo against their cheap artifacts like Vexing Bauble, Haywire Mite, and Soul-Guide Lantern, so it comes in as a flexible slot. Claws of Gix is the easiest cut since this matchup is about racing before their big Eldrazi or Ancient Stirrings engine takes over, not about incremental life gain.