where can I get mind control card?

Hi Everyone!
How to get 40 decks in this game?
I have only 36 decks and I can't play in challenge ..

PLEASE REPLY ..

Sorry I'm just new!
Can anyone help determine which is a better choice of cards.

1st
-- Crescendo OR Fangs of the Predator
2nd
-- Beetle Demon Bow OR Guardian's Oath
3rd
-- Wrath of Summer OR Voice of Winter
4th
-- Snow Sapphire OR Violet Thunderstorm
5th
-- Ogloth the Glutton OR Molten Destroyer

AND FINALLY!
6th
-- Victor ...

Pretty bland but effective deck.

Current Deck (42):

1 x Banebow

4 x Infernal Gargoyle
4 x Brutalis
4 x Death Mage Thaddeus
4 x Shadow Knight
2 x Ogloth the Glutton
(18 allies)

4 x Poison Arrow
3 x Here Be Monsters
4 x Shriek of Vengeance
2 x Sacrificial Lamb
2 x Ley Line Nexus
(15 abilities)

4 x Wrath of The Forest
4 x Soul Seeker
(8 items)

Demonstration ...

Current Deck (40):

1 x Serena Thoughtripper

2 x Dirk Saber
4 x Lily Rosecult
2 x Raven Wildheart
4 x Priest of The Light
4 x Nightshade
(16 allies)

3 x Assassination
2 x Sorcerous Poison
4 x Stop, Thief!
4 x Ill-Gotten Gains
(13 abilities)

1 x Night Prowler
3 x Black Garb
1 x Spelleater Bands
4 x Anklebreaker
1 x Dagger of Unmaking
(10 items)

Demonstration ...