Sauron, the Dark Lord is a 7/6 with ward sacrifice a legendary artifact or creature to target him
You can then tap the Crucible and remove storage counters to gain that much mana in any combination of colors - solely for casting Dragon spells or activating Dragon abilities
Adrestia Adventurer's Airship Aerial Surveyor Aethersphere Harvester Aetherwing, Golden-Scale Flagship Air Response Unit Apocalypse Runner Aradara Express Arcee, Acrobatic Coupe Avengers Quinjet Balamb Garden, Airborne Ballista Charger Bespoke Battlewagon Bessie, the Doctor's Roadster Big Wheel Bladewheel Chariot Blitzwing, Adaptive Assailant Bomat Bazaar Barge Boommobile Boosted Sloop Broadcast Rambler Brotherhood Vertibird Brute Suit Burner Rocket Capenna Express Captain America's Motorcycle Careening Mine Cart Cargo Ship Carriage of Dreams Carrion Cruiser Clamorous Ironclad Cloudspire Skycycle Clown Car Colossal Plow Conqueror's Galleon Consulate Dreadnought Cryptcaller Chariot Cultivator's Caravan Cybership Cyclonus, Cybertronian Fighter Damocles Base, Sword of Kang Daredevil Dragster Debris Beetle Deluxe Dragster Demolition Stomper Demonic Junker Dependable Quinjet Dermotaxi Detention Chariot Dodgy Jalopy Dragonfly Suit Dreadmobile Dune Drifter Dusk Legion Dreadnought Earthrumbler Enchanted Carriage Esika's Chariot Fell Flagship Filigree Racer Fire Nation Warship Flamewar, Streetwise Operative Fleetwheel Cruiser Flywheel Racer Foreboding Steamboat Funeral Longboat Futurist Sentinel Gastal Thrillroller Getaway Car Ghost Ark Gilded Assault Cart Goldbug, Scrappy Scout Golden Argosy
This alone would make Karlov a worthy Lifegain Commander, but it can also exile creatures at instant speed, in exchange for six +1/+1 counters
Mana Curve Even if you have an Elvish Mystic for turn one, you might still be able to lead with a Forest and find a convenient time to play Lumbering Falls later in the game
