* "Rainbow Dark Dragon" is a Synchro Monster. This means it's summoned using specific monsters and a Tuner monster. Fusion summoning is a different mechanic.
* "Rainbow Dark Dragon" has powerful effects. Its ability to negate spell/trap effects and destroy cards on the field makes it a formidable card, even without specific fusion support.
However, there are ways to utilize "Rainbow Dark Dragon" in a Fusion-based deck:
1. "Chaos Sorcerer": While not a direct fusion with "Rainbow Dark Dragon," "Chaos Sorcerer" is a powerful Chaos Fusion monster that can be summoned using multiple materials, including "Rainbow Dark Dragon." This allows you to combine its power with other Fusion monsters.
2. "The Chaos Creator": This card can Special Summon any Fusion Monster from your Extra Deck by banishing specific monsters from your graveyard, including "Rainbow Dark Dragon." This gives you flexibility in your Fusion strategy.
3. "Fusion Substitute": This card allows you to treat a monster on the field as a Fusion Material, meaning you could use "Rainbow Dark Dragon" as a material for a different Fusion Monster.
Ultimately, while there isn't a specific fusion monster using "Rainbow Dark Dragon" as a direct material, its powerful effects and synergy with other fusion-related cards make it a valuable asset in a fusion-based deck.