Rakdos Joins Up + Opalescence + Dack's Duplicate

Rakdos Joins Up

Opalescence

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 loop relies on the brilliant interaction between a legendary enchantment and a clone that can copy it. When you cast Dack's Duplicate, you have it enter the battlefield as a copy of Rakdos Joins Up, which simultaneously turns on Opalescence to make all non-Aura enchantments into creatures. Because Dack's Duplicate is now a legendary enchantment creature copy of Rakdos Joins Up, the legend rule instantly puts it into your graveyard, triggering both its own copy of the recursion ability and the original Rakdos Joins Up's damage-dealing ability. As Dack's Duplicate returns to the battlefield—bolstered by two +1/+1 counters—it immediately loops the legend rule again, allowing you to repeatedly trigger the death-and-return cycle to blast an opponent for lethal damage.