Activate up to five lands by tapping them, adding at least 4.
Cast Peregrine Drake by paying its mana cost.
When Peregrine Drake enters, it triggers twice. Resolve the first trigger, untapping five lands.
Holding priority, activate up to five lands by tapping them, adding at least 4.
Resolve the second Peregrine Drake trigger, untapping five lands.
Cast Spider-Man 2099 by paying its mana cost.
When Spider-Man 2099 enters, it triggers twice, returning it and Peregrine Drake from the battlefield to your hand.
Repeat.
This dazzling loop lets you generate infinite enter-the-battlefield and leave-the-battlefield triggers by leveraging the doubling power of Mirror Room // Fractured Realm. When you cast Peregrine Drake, the enchantment's static ability causes its untap trigger to happen twice, generating an excess of mana from your lands to fuel the engine. Once you have enough mana, you can cast Spider-Man 2099; its entrance also doubles up, allowing you to bounce both itself and the Peregrine Drake right back to your hand so you can repeat the entire cycle endlessly.