And if you only have Copperajah ex on your bench (or any Terastal Pokemon), none will take damage from the active Copperajahs attack!
Art that comes alive

Here's a list of cards you can get, as of December 2017: All legendary cards originally printed in Legends , Ice Age , or Homelands ther Vial Aetherworks Marvel Ali from Cairo Ancestral Recall Ancestral Vision Ancient Den Ancient Tomb Arcbound Ravager Balance Bazaar of Baghdad Berserk Biorhythm Birthing Pod Bitterblossom Black Lotus Black Vise Blazing Shoal Bloodbraid Elf Braids, Cabal Minion Braingeyser Brainstorm Burning Wish Candelabra of Tawnos Chalice of the Void Channel Chaos Orb Chrome Mox Cloud of Faeries Cloudpost Coalition Victory Copy Artifact Crop Rotation Cursed Scroll Dark Depths Dark Ritual Darksteel Citadel Deathrite Shaman Demonic Consultation Demonic Tutor Dig Through Time Dingus Egg Disciple of the Vault Divine Intervention Doomsday Dread Return Dream Halls Earthcraft Empty the Warrens Emrakul, the Aeons Torn Emrakul, the Promised End Enlightened Tutor Entomb Erayo, Soratami Ascendant Eye of Ugin Fact or Fiction Falling Star Fastbond Felidar Guardian Feldon's Cane Flash Fluctuator Fork Frantic Search Gaea's Cradle Gauntlet of Might Gifts Ungiven Gitaxian Probe Glimpse of Nature Goblin Lackey Goblin Recruiter Golgari Grave-Troll Grapeshot Great Furnace Green Sun's Zenith Grim Monolith Gush Hermit Druid Hurkyl's Recall Hymn to Tourach Hypergenesis Hypnotic Specter Icy Manipulator Illusionary Mask Imperial Seal Intangible Virtue Invigorate Ivory Tower Jace, the Mind Sculptor Juggernaut Karakas Kird Ape Land Tax Leovold, Emissary of Trest Library of Alexandria Limited Resources Lin Sivvi, Defiant Hero Lingering Souls Lion's Eye Diamond Lodestone Golem Lotus Petal Mana Crypt Mana Drain Mana Vault Maze of Ith Memory Jar Mental Misstep Merchant Scroll Metalworker Mind Over Matter Mind Twist Mind's Desire Mirror Universe Mishra's Workshop Monastery Mentor Mox Diamond Mox Emerald Mox Jet Mox Pearl Mox Ruby Mox Sapphire Mystical Tutor Necropotence Oath of Druids Orcish Oriflamme Painter's Servant Panoptic Mirror Peregrine Drake Personal Tutor Ponder Preordain Primeval Titan Prophet of Kruphix Punishing Fire Recall Recurring Nightmare Reflector Mage Regrowth Replenish Rishadan Port Rite of Flame Rofellos, Llanowar Emissary Rukh Egg Seat of the Synod Second Sunrise Seething Song Sensei's Divining Top Serendib Efreet Serra's Sanctum Shahrazad Skullclamp Smuggler's Copter Sol Ring Splinter Twin Squandered Resources Stoneforge Mystic Strip Mine Stroke of Genius Summer Bloom Sundering Titan Survival of the Fittest Sway of the Stars Sword of the Ages Sword of the Meek Sylvan Primordial Temporal Fissure Thawing Glaciers Thirst for Knowledge Thorn of Amethyst Time Spiral Time Vault Time Walk Timetwister Tinker Tolarian Academy Trade Secrets Treasure Cruise Tree of Tales Trinisphere Umezawa's Jitte Underworld Dreams Upheaval Valakut, the Molten Pinnacle Vampiric Tutor Vault of Whispers Voltaic Key Wheel of Fortune Wild Nacatl Windfall Worldfire Worldgorger Dragon Yawgmoth's Bargain Yawgmoth's Will Zuran Orb This list also includes all cards with the card type conspiracy, but they only work from the command zone, so really don't bother

As Wizards mentioned in March of the Machines release notes, the 36 sieges are only the first version of battle cards
The requirement monster is Aria for a couple reasons - a slight upgrade to Aria's anti-targeting effect (Aria blocks targeting from both players) and to make it a little more difficult to have this and Aria on the field without extra assistance.