Dualcaster Mage + Black Sun's Twilight

Dualcaster Mage
Black Sun's Twilight

Requires
Dualcaster Mage must be in hand. Black Sun's Twilight must be in hand. Mana needed: 6brr
Steps
  1. Cast Black Sun's Twilight with X equal to 5 by paying 5b.
  2. In response, cast Dualcaster Mage by paying 1rr.
  3. Dualcaster Mage enters the battlefield, copying Black Sun's Twilight targeting itself.
  4. Resolve that copy, putting Dualcaster Mage into the graveyard and then returning it to the battlefield.
  5. Repeat from step 3.
Results
Infinite death triggers. Infinite ETB. Infinite LTB. Infinite magecraft triggers.