When Phantom Steed enters the battlefield, its first ability triggers, exiling Abdel Adrian until Phantom Steed leaves the battlefield.
Abdel Adrian leaves the battlefield, ending its effect, causing Spark Double to return from exile to the battlefield as a copy of Phantom Steed.
When Spark Double enters the battlefield, its first ability triggers, exiling Phantom Steed until Spark Double leaves the battlefield.
Phantom Steed leaves the battlefield, ending its effect, causing Abdel Adrian to return from exile to the battlefield.
When Abdel Adrian enters the battlefield, it triggers, exiling Spark Double and any number of other nonland permanents you control until Abdel Adrian leaves the battlefield and creating at least one 1/1 Soldier creature token.
Spark Double leaves the battlefield, ending its effect, causing Phantom Steed to return to the battlefield from exile.
Repeat from step 2.
This mesmerizing loop turns a clever recursive dance into an endless parade of value, keeping your board perpetually cycling through the ether. By leveraging Spark Double to ignore the legend rule and copy Phantom Steed, you create a stepping stone that constantly alternates exiling duties with Abdel Adrian, Gorion's Ward. Every time the pieces trade places in exile, Abdel Adrian's entry triggers flood your board with an endless army of Soldier tokens while infinitely repeating all of your nonland permanents' enter-the-battlefield abilities.