Sakashima the Impostor, Starfield of Nyx, and Detention Sphere

Prerequisites

• Sakashima the Impostor in hand
• Starfield of Nyx on the battlefield
• Detention Sphere on the battlefield
• available

Steps

1. Cast Sakashima the Impostor by paying , having it enter the battlefield as a copy of Detention Sphere that is a 3/3 legendary enchantment creature named Sakishima the Imposter
2. When Sakashima the Impostor, it triggers its first ability from Detention Sphere, exiling itself
3. Sakashima the Impostor leaves the battlefield, triggering its second ability from Detention Sphere, returning itself to the battlefield as a copy of Detention Sphere that is a 3/3 legendary creature named Sakashima the Impostor
4. Repeat from step 2 any number of times
5. End the loop by choosing a different creature to copy or a different permanent to exile, or by declining to exile anything

Results

• Infinite ETB
• Infinite LTB