Card Rulings:Archfiend of Gilfer
Mentions in Other Rulings
- Bone Temple Block: Discarding a card is part of the resolution of “Bone Temple Block.” The effects of “Bone Temple Block” happen in sequence, so if you discard “Archfiend of Gilfer,” it will miss the timing on and not activate its effect.
- Machina Fortress: Your opponent will miss the timing to activate the effect of “Archfiend of Gilfer” if it is discarded by the effect of “Machina Fortress.”
- Power Tool Dragon: If “Macro Cosmos” is active, you can still send an Equip Spell Card to the Graveyard to protect “Power Tool Dragon.” If a Chain resolves with “Power Tool Dragon” being destroyed, and you send “Archfiend of Gilfer” equipped to “Power Tool Dragon” to the Graveyard instead, you can activate the effect of “Archfiend of Gilfer” and re-equip it to a monster on the field (including “Power Tool Dragon”). If you send “Archfiend of Gilfer” equipped to “Power Tool Dragon” to the Graveyard during the middle of a Chain, or in the middle of an effect resolution, then you cannot activate “Archfiend of Gilfer” and reequip it, because you missed the timing.
- If an "Archfiend of Gilfer" which is equipped to a monster is destroyed by "Mystical Space Typhoon" during the Battle Step, then you can use its effect to equip it to another monster. However, "Mystical Space Typhoon" cannot be activated to destroy "Archfiend of Gilfer" if you have already entered the Damage Step.
Mentions in Other Rulings
- Bone Temple Block: "Discard one card" is done at the resolution of "Bone Temple Block", but not at the same time that the monsters are Special Summoned. If you discard "Archfiend of Gilfer", then you cannot activate its effect.
- Destruct Potion: The effect of "Destruct Potion" which destroys the monster and the effect which recovers Life Points are treated as resolving simultaneously.
- Roar of the Earthbound Immortal: For "Roar of the Earthbound Immortal", "destroy one attacking monster" and "inflict damage to your opponent's Life Points equal to half of the ATK of the destroyed monster" are considered to resolve simultaneously.
Previously Official Rulings
These TCG rulings were issued by Upper Deck Entertainment and have since been declared unofficial by Konami. They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: 
- Konami FAQ: Can I destroy my equipped "Archfiend of Gilfer" when my opponent declares an attack to equip it to the attacking monster?
- Konami FAQ: Please explain the effect of "Bone Temple Block".
- Konami FAQ: Are the "destroy" and "recover" effects of "Destruct Potion" treated as resolving simultaneously?
- Konami FAQ: Are the effect of "Roar of the Earthbound Immortal" which destroys and the effect of "Roar of the Earthbound Immortal" which inflicts damage considered to resolve simultaneously?
- Konami Judge Program Forum: Individual Email Rulings VS Individual Card Rulings
- UDE FAQ: Individual Card Rulings [A-C]
- UDE FAQ: Individual Card Rulings [D-E]
- UDE FAQ: Individual Card Rulings [F-H]
- UDE FAQ: Individual Card Rulings [I-K]
- UDE FAQ: Individual Card Rulings [L-O]
- UDE FAQ: Individual Card Rulings [P-R]
- UDE FAQ: Individual Card Rulings [S-T]
- UDE FAQ: Individual Card Rulings [U-Z]
- UDE FAQ: SPECIFIC CARDS RULINGS