There's other stuff I wanted to go over, but I'm a bit lazy to do all that extra work right now, so....
The way the Egyptian Gods work with their mechanical resistances/immunities is... strange. IIRC, spells are often treated as only affecting them for 1 turn, if they work on them at all. Supposedly.
During Strings vs Yugi, Strings activates Nightmare's Steelcage 1 turn before he summons Slifer. Since it lasts 2 of the opponent's turns, NSC was present when Slifer was summoned. Dialogue might be worth checking here, as Yugi also had Buster Blader out at the time, who had just barely higher attack, but.... Although it is notable that NSC prevents Slifer's second mouth firing on Kuriboh, as the anime treats it as a "special attack".
So apparently a Spell Card CAN prevent a God from attacking, as Slifer couldn't use its Special Attack, its Second Mouth, while NSC was out.
Original dialogue should be checked to see the stance on Brain Control. Ex: If Strings taunted Yugi about how BC may not work on Slifer before Yugi revealed he was targeting Revival Jam instead.
Monster Reborn often seems to work on Egyptian Gods, but supposedly only lasts 1 turn on them.
Notably, in Yugi vs Kaiba, the Gods' immunities seem to get ignored a little:
Command Silencer is used to make Slifer unable to hear Yugi's commands, thus, making it unable to attack.
Also from that duel, Necromancy, which has an effect where if 1 of the monsters it revived for your opponent gets destroyed, their other monsters lose 600 ATK each time 1 of the Necromancy'd monsters gets destroyed. Thus, Obelisk lost 2,400 ATK to this Spell, but regained it at the end of the turn. Necromancy's ATK change effect has never been shown to work for 1 turn, however, even when not used on a God.
Sword of Soul, upon being destroyed, is able to use its effect on Obelisk to give it more ATK. So much for being immune to other monsters' effects?
We also have Yugi vs Bakura; the Ghost of Dark Sanctuary is treated as an Equip Card, since it's able to be removed through Collected Power & Exile of the Wicked. Equip Cards are typically spells, & it originates from a Field Spell, but it's also possible for Traps to be equipped to stuff. Not sure how common that is in the anime, though.
What matters is that Slifer is apparently immune to this "The Ghost of Dark Sanctuary" equip thing.
Dialogue would need to be checked, but it may also have shown trap immunity. Bakura had been using his re-usable (Flips itself face-down after activation) Dark Spirit of the Silent Trap all duel. He doesn't bother using it against Slifer... but then again, its effect is to Negate 1 attack & force a different monster to attack. With Slifer as Yugi's lone monster & being immune to TGoDS, there would be no point to using it there.
Trap Immunity seems to be a little more clear cut. Obelisk punches through Mirror Force... but then we get the absurdity of Ishizu vs Kaiba. Ishizu should be knowledgeable on Obelisk, since she knows a good bit about the Gods & held Obelisk in safekeeping, & expected it returned.
But her whole strategy hinges on Blast Held by a Tribute, a TRAP card. Also called
Sacrifice's Blast . Its remarkably ridiculous in how it works in the anime, too, IMHO:
With BHbaT/SB, you plant a bomb in a monster, so that if something Tribute Summoned using your target attacks, you activate this, & the attacker, gets destroyed & its ATK is dealt as damage to the player.
Yes. Anime Sacrifice's Blast is a card where to plant the bomb, you have to do it while the card is face-down, WITHOUT turning it face-up, and WITHOUT telling your opponent your target. Only when the tribute summoned attacker attacks do you flip it up.
Either way, Ishizu of all people planning to beat Kaiba by using this to plant a bomb in Obelisk to destroy it & him puts the trap immunity into question. That said, we never see the results of this attempt because Kaiba decides to summon BEWD instead, defying her Precognition.
The trap immunity is also called into question by Metal Reflect Slime. Despite being a Trap (Which turns into a Monster), it manages to copy Obelisk's appearance. But this has no presence on game mechanics, which would suggest it's just the anime's game not only following GMs.
Arguably, there's also
Magnet Force; In Yugi vs Atem, Yugi uses it so that every time Slifer's Second Mouth Special Attack triggers against one of his Magnet Warriors, he can have it be redirected. In this case, to other Gods.
So Slifer's "Special Attack" can be redirected, according to that.
Lastly, the "Spell Cards only last on them for 1 turn" bit is called into question by Gurimo using Obelisk with the Seal of Orichalcos; The Field Spell's ATK increase sticks to Obelisk, as does the Orichalcos's effects. But supposedly, their types of magic don't mix & the anime claimed the Orichalcos's magic was older & stronger or such, IIRC.
Hope this helps & that I ain't bothering you too much.
