Rakdos Joins Up + Starfield of Nyx + Dack's Duplicate

Rakdos Joins Up

Starfield of Nyx

Dack's Duplicate

How it works

1. Cast Dack's Duplicate by paying its mana cost. Choose to have it enter the battlefield as a copy of Rakdos Joins Up.
2. Put Dack's Duplicate into your graveyard due to the legend rule.
3. Dack's Duplicate's first ability and second ability trigger, along with Rakdos Joins Up's second ability.
4. Resolve Dack's Duplicate's second trigger and Rakdos Joins Up's trigger, dealing damage to target opponent.
5. Resolve Dack's Duplicate's first trigger, returning it from your graveyard to the battlefield with two +1/+1 counters on it as a copy of Rakdos Joins Up.
6. Repeat from step 2.

This clever loop turns the legend rule into a lethal weapon by using Rakdos Joins Up to continuously resurrect itself through a clever bit of identity-theft. When you cast Dack's Duplicate and have it enter as a copy of Rakdos Joins Up, state-based actions immediately send one to the graveyard, but not before its own enters-the-battlefield trigger sets up an endless cycle. That trigger lets you target the very same Dack's Duplicate in your graveyard, returning it to the battlefield with two additional +1/+1 counters to restart the whole process while dealing damage to your opponent along the way. While Starfield of Nyx isn't strictly necessary for the core loop to fire off its infinite damage and death triggers, it provides a gorgeous mechanical home and alternate recursion engine for your enchantments should you need it.