The catch is that you have to have a Dragon to tap it
Game packs were sold for $19.99 USD

3 4,499decks Chainer, Nightmare Adept 3,367decks Mishra, Claimed by Gix 2,993decks Wort, Boggart Auntie 2,915decks Olivia, Crimson Bride 2,775decks The Scorpion God 2,658decks Olivia Voldaren 2,612decks Kroxa, Titan of Death's Hunger 2,525decks Tor Wauki the Younger 2,416decks Karazikar, the Eye Tyrant 2,387decks Sethron, Hurloon General 2,334decks Syrix, Carrier of the Flame 2,265decks Akul the Unrepentant 2,225decks Zoyowa Lava-Tongue 2,153decks The Balrog, Durin's Bane 2,147decks Totentanz, Swarm Piper 1,885decks Mahadi, Emporium Master 1,861decks Garna, Bloodfist of Keld 1,793decks Obosh, the Preypiercer 1,781decks Bladewing, Deathless Tyrant 1,747decks Setzer, Wandering Gambler 1,741decks Ares, God of War 1,683decks Anje, Maid of Dishonor 1,645decks Valki, God of Lies 1,642decks Kaervek the Merciless 1,592decks Rograkh, Son of Rohgahh // Tevesh Szat, Doom of Fools 1,520decks Ayara, Widow of the Realm 1,482decks Rohgahh, Kher Keep Overlord 1,475decks Kefka, Dancing Mad 1,394decks Far Fortune, End Boss 1,365decks Rakdos, the Showstopper 1,355decks Flamewar, Brash Veteran 1,338decks Lagomos, Hand of Hatred 1,327decks Judith, the Scourge Diva 1,281decks Greven, Predator Captain 1,256decks Hidetsugu, Devouring Chaos 1,237decks Gut, True Soul Zealot // Agent of the Iron Throne 1,155decks Rakdos, Patron of Chaos 1,135decks Locke, Treasure Hunter 1,133decks Smaug the Impenetrable 1,132decks Mishra, Tamer of Mak Fawa 1,120decks Florian, Voldaren Scion 1,074decks Olivia, Mobilized for War 1,041decks Shagrat, Loot Bearer 996decks Lucius the Eternal 976decks Kethek, Crucible Goliath 960decks Witch-king, Sky Scourge 941decks Green Goblin, Nemesis 933decks Neheb, the Worthy 925decks Malfegor 923decks Fire Lord Ozai 920decks Kalain, Reclusive Painter 890decks Tokka & Rahzar, Terrible Twos 870decks Krark, the Thumbless // Vial Smasher the Fierce 843decks Carnage, Crimson Chaos 827decks Gut, True Soul Zealot // Haunted One 746decks The Beast, Deathless Prince 719decks Kellogg, Dangerous Mind 712decks Ultimate Green Goblin 688decks Zagras, Thief of Heartbeats 664decks Uglk of the White Hand 626decks The Dalek Emperor 625decks Kamber, the Plunderer // Laurine, the Diversion 618decks Karlach, Fury of Avernus // Cultist of the Absolute 606decks Bladewing the Risen 603decks Barktooth Warbeard 599decks Garland, Knight of Cornelia 586decks Rankle and Torbran 572decks

Creatures are permanents, meaning they stay on the battlefield until they are destroyed or otherwise removed from the game
Sure, you need to be able to generate all five colors of mana to make the most of it, but that shouldnt be too much of a problem given Explorers excellent mana base
I checked over the list multiple times and I feel like the only two cards that don't synergize and I feel are a bit weak as generic filler is Pull from Tomorrow and Destroy Evil