Eternal Card Game

The type of unit is marked on the bottom of cards in Eternal. For this, you want to play cards that have this marking on the card. By default, the Justice (green) deck offers the most soldiers to start out with. Combined with Rolant's ability(the default Justice Scion), which plays two soldiers each time you attack, this should come pretty easily, but it can be sped up by battling in the gauntlet, and drawing out the game until you get Rolant. At this point, just try to maximize his attacks while minimizing the damage done to the AI, which should get you two new soldiers each turn. If you run out of room, just replace soldiers with more soldiers, and continue until you unlock this or win.