To gain access go to Grandfather's Card Shop (two screens down from the clocks square), go to the computer (little black thing) on the very right side of the room. You will be asked if you wish to enter a password for the price of 1,000 Domino. Say "Yes" and enter a eight digit password. This can give you access to some very powerful cards.
 
Card Password
7 Colored Fish 23771716

Abyss Flower 40387124

Acid Crawler 77568553

Acid Trap Hole 41356845

Air Marmot Of Nefa 75889523

Akakieisu 38035986

Akihiron 36904469
Alinsection 70924884

Alligator's Sword 64428736

All-Seeing Goddess 53493204

Alpha The Magnet Warrior 99785935

Amazon Of The Seasons 17968114

Amazon Sword Women 94004268

Ameba 95174353
Amphibious Bugroth 40173854

Ancient Brain 42431843

Ancient Elf 93221206

Ancient Jar 81492226

Ancient One of the Forest 14015067

Ancient Sorcerer 36821538

Ancient Tool 49587396

Ancient Tree of Enlightenment 86421986

Ancient Water Turtle 11714098

Angelwitch 37160778

Ansatsu 48365709
Anthrosaurus 89904598

Anti Raigeki 42364257

Aqua Dragon 86164529

Aqua Madoor 85639257

Aqua Snake 12436646

Arlownay 14708569
Arma Knight 36151751

Armaill 53153481
Armed Ninja 09076207

Armored Lizard 15480588

Armored Rat 16246527

Armored Starfish 17535588

Armored Zombie 20277860

Axe of Despair 40619825

Axe Raider 48305365

Baby Dragon 88819587

Barox 06840573
Barrel Dragon 81480460

Barrel Lily 67841515

Barrel Rock 10476868

Basic Insect 89091579

Bat 72076281
Battle Ox 05053103

Battle Steer 18246479

Battle Warrior 55550921

Beaked Snake 06103114

Bean Soldier 84990171

Bear Trap 78977532

Beast Fangs 46009906

Beast King of the South 99426834

Beast of Talwar 11761845

Beastly Mirror Ritual 81933259

Beautiful Beast Trainer 29616941

Beautiful Headhunter 16899564

Beaver Warrior 32452818

Behegon 94022093
Berfomet 77207191
Beta the Magnet Warrior 39256679

Bickuribox 25655502

Big Eye 16768387
Big Insect 53606874

Big Shield Gardna 65240384

Binding Chain 08058240

Bio Plant 07670542

Bite Shoes 50122883

Black Dragon Jungle 89832901

Black Illusion Ritual 41426869

Black Luster Ritual 55761792

Black Luster Soldier 05405694

Black Pendant 65169794

Black Skull Dragon 11901678

Blackland Fire Dragon 87564352

Bladefly 28470714