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 Detention Sphere to return from exile to the battlefield.
When Detention Sphere enters the battlefield, its first ability triggers, exiling Phantom Steed.
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 Detention Sphere 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.
When Detention Sphere leaves the battlefield, its second ability triggers, returning Phantom Steed to the battlefield from exile.
Repeat from step 2.
Results
Infinite blinking of nonland permanents you control.