Five-Color Mono-Black is right in the range of possible
Not only are these cards powerful, but they really make it stand out from other Commander decks and strengthen the 40K theme by being originals for the deck

Animated Army Commander: (1) Creatures: (21) Llanowar Loamspeaker Lotus Cobra Sakura-Tribe Elder Trailtracker Scout Wandertale Mentor Burnished Hart Grumgully, the Generous Prosperous Bandit Brightcap Badger Goreclaw, Terror of Qal Sisma Teapot Slinger Evercoat Ursine Garruk's Packleader Grothama, All-Devouring Pyreswipe Hawk Tendershoot Dryad Wildsear, Scouring Maw Etali, Primal Storm Kodama of the East Tree Rampaging Baloths Ghalta, Primal Hunger Planeswalkers: (1) Instants: (4) Abrade Beast Within Chaos Warp Big Score Sorceries: (8) Explore Farseek Rampant Growth Starstorm Cultivate Decimate Harmonize Blasphemous Act Artifacts: (14) Sol Ring Arcane Signet Fellwar Stone Gruul Signet Mind Stone Talisman of Impulse Thought Vessel Esika's Chariot Hedron Archive Thran Dynamo Gilded Lotus Bootleggers' Stash Rolling Hamsphere Spine of Ish Sah Enchantments: (13) Garruk's Uprising Alchemist's Talent Greater Good Outpost Siege Path of Discovery Berserkers' Onslaught Gratuitous Violence Rain of Riches Thickest in the Thicket Unnatural Growth Primeval Bounty Sunbird's Invocation Warstorm Surge Lands: (38) Cinder Glade Command Tower Copperline Gorge Evolving Wilds Exotic Orchard Forest x10 Forgotten Cave Game Trail Gruul Turf Karplusan Forest Mossfire Valley Mosswort Bridge Mountain x8 Path of Ancestry Raging Ravine Reliquary Tower Rootbound Crag Sheltered Thicket Temple of Abandon Terramorphic Expanse Tranquil Thicket Wooded Ridgeline Commander, Theme, and Strategy This deck's Gruul commander is Bello, Bard of the Brambles

Whether youre the classic Tatyova, Benthic Druid, the scary Aesi, Tyrant of Gyre Strait, or doing the full-house with Omnath, Locus of Creation, fetchable lands are the bread and butter of your decks
Is Cycling an Ability
Even decks that you would assume would really want it, like Izzet Murktide, only play a couple of copies, so I'm not sure how much Preordain would really change