If the face-down creature was an instant or sorcery card, it cant return to the battlefield and simply stays exiled
Having ways to protect your commander that can be customized to meet your needs is just comfortable
Stinkweed Imp is pretty strong alongside Faithless Looting, but a single dredge can fuel multiple delve spells over the next few turns

Commander| Jason Alt Commander (2) 1 Ludevic, Necro-Alchemist 1 Vial Smasher the Fierce Creatures (18) 1 Archaeomancer 1 Chasm Skulker 1 Fog Bank 1 Guttersnipe 1 Jeleva, Nephalia's Scourge 1 Jori En, Ruin Diver 1 Kaervek the Merciless 1 Melek, Izzet Paragon 1 Niv-Mizzet, the Firemind 1 Mulldrifter 1 Notion Thief 1 Psychosis Crawler 1 Shriekmaw 1 Snapcaster Mage 1 Spitebellows 1 Taurean Mauler 1 Tidespout Tyrant 1 Torrential Gearhulk Planeswalkers (1) 1 Nicol Bolas, Planeswalker Instants (7) 1 Curtains' Call 1 Dig Through Time 1 Evacuation 1 Mindswipe 1 Murderous Cut 1 Rewind 1 Searing Wind Sorceries (11) 1 Black Sun's Zenith 1 Blasphemous Act 1 Call the Skybreaker 1 Cruel Ultimatum 1 Decree of Pain 1 Mizzix's Mastery 1 Spelltwine 1 Subterranean Tremors 1 Temporal Tresspass 1 Treasure Cruise 1 Volcanic Vision Enchantments (8) 1 Curse of Echoes 1 Eye of the Storm 1 Future Sight 1 Gratuitous Violence 1 Meishin, the Mind Cage 1 Mind's Dilation 1 Possibility Storm 1 Thought Reflection Artifacts (15) 1 Chromatic Lantern 1 Coalition Relic 1 Commander's Sphere 1 Crawlspace 1 Darksteel Ingot 1 Dimir Signet 1 Expedition Map 1 Izzet Signet 1 Pyromancer's Goggles 1 Rakdos Signet 1 Sol Ring 1 Sphinx-Bone Wand 1 Thought Vessel 1 Venser's Journal 1 Wayfarer's Bauble Lands (38) 6 Island 6 Mountain 6 Swamp 1 Ash Barrens 1 Bloodstained Mire 1 Command Tower 1 Crumbling Necropolis 1 Desolate Lighthouse 1 Dimir Aqueduct 1 Evolving Wilds 1 Exotic Orchard 1 Grixis Panorama 1 Izzet Boilerworks 1 Polluted Delta 1 Rakdos Carnarium 1 Reliquary Tower 1 River of Tears 1 Scalding Tarn 1 Temple of Deceit 1 Temple of Epiphany 1 Temple of Malice 1 Temple of the False God 1 Terramorphic Expanse Rocky Tar Pit and noise like that

Hexproof hasnt made its presence known yet, but I think that with a better build and better plans for the metagame, Hexproof could really take advantage of a field that isnt ready for it
In Wilds of Eldraine , you'll be able to find these special full-art lands with fairy talethemed artwork