* Titan Firestorm's Activation Condition: "Titan Firestorm" requires you to have 3 or more "Fire" monsters in your Graveyard. This means you need to have already summoned and destroyed "Fire" monsters.
* Egyptian God Cards and Summoning: The Egyptian God Cards (Slifer the Sky Dragon, Obelisk the Tormentor, and The Winged Dragon of Ra) are powerful monsters with their own summoning conditions. They are not typically considered "Fire" monsters and are often summoned with special effects or tributes.
* Tribute Summoning and "Fire" Monsters: While you can use a "Fire" monster as a tribute to summon an Egyptian God Card, it won't fulfill the requirement of having 3 or more "Fire" monsters in your Graveyard for "Titan Firestorm".
In Conclusion: You can't directly use the Egyptian God Cards to activate "Titan Firestorm". You'd need to rely on other "Fire" monsters to fulfill the activation condition and then summon your Egyptian God Cards afterward.