Astral Dragon, Mirror Image, and Necromancy

Prerequisites

• Astral Dragon in your graveyard
• Mirror Image in your graveyard
• Necromancy in hand
• available

Steps

1. Cast Necromancy by paying
2. When Necromancy enters the battlefield, it triggers, returning Astral Dragon from your graveyard to the battlefield, and then attaching Necromancy to Astral Dragon
3. When Astral Dragon enters the battlefield, it triggers, creating two token copies of Necromancy that are 3/3 Dragon creatures in addition to their other types
4. When the Necromancy tokens enter the battlefield, they trigger, with at least one trigger targeting Mirror Image
5. Resolve the first Necromancy trigger, returning Mirror Image from your graveyard to the battlefield as a copy of Astral Dragon, and not attaching Necromancy to Mirror Image due to Necromancy being a creature
6. The Necromancy Aura creature token is put into your graveyard as a state-based action due to being an Aura that is unattached
7. The Necromancy token leaves-the-battlefield ability triggers, as well as Mirror Image's enters-the-battlefield ability
8. Resolve the Necromancy trigger, causing you to sacrifce Mirror Image
9. Resolve the Mirror Image trigger, creating two token copies of Necromancy that are 3/3 Dragon creatures in addition to their other types
10. Repeat from step 4

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers