Instructions
Throw any card as the first, but do not land near the middle. This gives you time to explore the field. One of Marduk's plans in battle is to use Darkus Phantom, which absorbs your power and adds it to its own. By missing the first throw, Marduk is at a disadvantage.
Throw out your next card as normal, fighting Marduk as normal. Marduk will throw out one of his cards and attempt to do damage, but without the extra power, he will fail, giving you a gate card.
Repeat the previous two steps until you defeat Marduk. You win the game once you receive three gate cards.