If you have 2 “Goblin Kings”, or a “Goblin King” equipped with “Raregold Armor” and another Fiend-Type monster, your opponent cannot attack.
“Goblin King”’s second effect includes Fiend-Type monsters on your opponent’s side of the field.
Face-down Fiend-Type monsters are not included for “Goblin King”’s second effect.
If you equip “Megamorph” to “Goblin King”, “Goblin King”’s ATK is 0.
If you have a Fiend-Type monster and a face-down “Goblin King”, and “Goblin King” is attacked, “Goblin King”’s ATK and DEF increase after he’s flipped face-up, but before damage calculation is applied.