Aardwolf's Advantage Abandon the Post Acceptable Losses Acidic Soil Act of Treason Act on Impulse Aftershock Agate Assault Alchemist's Gambit Alchemist's Greeting Allure of the Unknown Alpha Brawl Amped Up Anarchy Ancestral Anger Angelfire Ignition Anger of the Gods Angrath's Fury Angrath's Rampage Anzrag's Rampage Apex of Power Apocalypse Arc Blade Arc Lightning Arc Trail Archaic's Agony Armed // Dangerous Arrow Storm Art Appreciation Artistic Process Asgardian Inspiration Assault // Battery Assault Strobe Assault on Osgiliath Avacyn's Judgment Avalanche Avengers Disassembled Awaken the Blood Avatar Awaken the Sleeper Awe for the Guilds Banefire Barrage of Boulders Bathe in Dragonfire Beacon Bolt Beastie Beatdown Become Brutes Begin the Invasion Bend or Break Besmirch Bionic Blow Blasphemous Act Blast of Genius Blaze Blazing Volley Blightning Blinding Flare Blood Feud Bloodsoaked Insight Bloody Betrayal Blow Your House Down Boiling Earth Boiling Seas Bolt of Keranos Boltwave Bond of Passion Bonfire of the Damned Bonus Round Book Burning Boom // Bust Borrowed Knowledge Bot Bashing Time

Because The Master, Multiplied was only printed in one set (where you could either find it in a $50 Commander precon or in $20-$30 Collector packs), the supply for this card has always been low
Wherever you have gigantic, powerful creatures with wild abilities, you'll see demand
And because these exclusives often hold their mystique, they can become quite valuable
Then, unless you're somehow in first place on land count, it'll let you cheat those lands into play too
Consequently, it's no surprise that this card was banned in the modern format given the myriad opportunities to exploit it with cards printed in the past as well as cards yet to come