Abdel Adrian enters the battlefield, exiling Spark Double until Abdel Adrian leaves the battlefield, and creating a 1/1 Soldier creature token.
Spark Double leaves the battlefield, triggering its second ability, returning Fiend Hunter from exile to the battlefield.
Fiend Hunter enters the battlefield, triggering its first ability, exiling Abdel Adrian.
Abdel Adrian leaves the battlefield, returning Spark Double from exile to the battlefield as a copy of Fiend Hunter.
Spark Double enters the battlefield, triggering its first ability, exiling Fiend Hunter.
Fiend Hunter leaves the battlefield, triggering its second ability, returning Abdel Adrian from exile to the battlefield.
Repeat from step 2.
This elegant loop relies on Abdel Adrian, Gorion's Ward to continuously exile and recast your board via a revolving door of triggers. Spark Double enters as a non-legendary copy of Fiend Hunter, allowing it to safely exile Abdel Adrian without triggering the legendary rule, while the real Fiend Hunter joins the dance to keep the chain reaction infinitely looping. Every single iteration of this cycle resets your permanents, generating an endless army of Soldier tokens alongside infinite entry and exit triggers to overwhelm your opponents.