Fusion monsters require two or more specific monsters to be in play under your control at the same time, at which point you may use the "Fusion Material" card to fuse them into a stronger monster. For example, you can summon the "Black Land Fire Dragon" after you have both "Wretches Ghost" and "Yamatano Dragon Scroll" in play.
In "Yu-Gi-Oh! Dark Duel Stories," you play the part of a spell caster with legions of monsters and a near-limitless amount of spells and traps, all of which are used to defeat your opponents. "Duel Stories" features 50 Fusion monsters that you can summon to your side after meeting specific game play criteria. Mastering how to use your summons effectively is the key to winning duels.
Early in the game, you have access to fewer game-winning cards. As you defeat your opponents, you unlock new, more powerful cards to add to your deck. Fusion monsters bridge the gap between the early and later stages in the game by giving you access to stronger monsters at the expense of your weaker monsters. While individually the "Time Wizard" and "Baby Dragon" cards are offensively weak and don't provide a strong defense, together they fuse into the "Thousand Dragon," which boasts a whopping 2,400 attack points and 2,000 defense points.
Some Fusion monsters may be summoned using multiple sets of card combinations. You summon the "Jungle Dragon" by fusing the "Petit Dragon" and "Rainbow Flower"; the "Spike Seadra" and "Abyss Flower"; or the "Darkworld Thorns" and "Darkfire Dragon" cards. You summon the "Queen of the Autumn Leaf" to your side after fusing the "Enchanting Mermaid" with either the "Abyss Flower" or the "Green Forest King."
Just like individual monsters, Fusion monsters can be classified in subtypes. For example, you can utilize "Warrior," "Dragon" and "Fiend" subtypes when playing with a themed deck, which provides the opportunity for synergistic attacks against your opponent. Dragon-themed decks use creatures and spells that give bonuses to dragon creatures, while a warrior-themed deck employs support cards to make your warriors more effective in battle.