Advanced format ruling
Fiend Skull Dragon
Card effect (current official text)"Cave Dragon" + "Lesser Fiend"
(This card is always treated as an "Archfiend" card.)
A Fusion Summon of this card can only be done with the above Fusion Material Monsters. Negate the effects of Flip Effect Monsters. Negate any Trap effects that target this card on the field, and if you do, destroy that Trap Card.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.