Since Rise of the Floodborn features zero six-drops at common, the desirable ones are at an even higher premium if you would like to fill out your curve
UR Ultra Rare Red Blossoms from Underroot X DARK Level 1 [ FiendEffect ] ATK 0 DEF 0 If this card is in your hand: You can target 1 Spell/Trap in each GY
I think youre getting pretty solid value here, between getting some ramp and venturing into a dungeon
The cost reduction Jhoira's Familiar provides is good with legends, artifacts, sagas, and makes several loop combos viable like Mystic Forge + Sensei's Divining Top
Cards like Mystical Archive: Mizzix's Mastery or Tibalt, Cosmic Impostor could provide more value and versatility in gameplay compared to the Double-Faced Substitute Card, making them better options for inclusion in a deck
Entropic Uprising supports this heavily by running tons of Wheels (Runehorn Hellkite, Dragon Mage, Wheel of Fate, Windfall, Ancient Excavation, Whispering Madness) and then a bunch of ways to take advantage of all those discarded cards / filled graveyards with stuff that reward you for your opponents discarding (Nath of the Gilt-Leaf, Sangromancer, Waste Not) or for having filled graveyards (Guiltfeeder, Spellheart Chimera, Worm Harvest, Ghastly Conscription)
