Ratadrabik of Urborg + Leyline of Singularity + Dack's Duplicate

Ratadrabik of Urborg

Leyline of Singularity

Dack's Duplicate

How it works

1. Cast Dack's Duplicate by paying its mana cost. Choose to have it enter as a copy of Ratadrabik.
2. Put Dack's Duplicate into your graveyard due to the legend rule.
3. When Dack's Duplicate dies, Ratadrabik triggers, creating a token copy of Dack's Duplicate that is a copy of Ratadrabik but is a 2/2 Zombie in addition to its other types.
4. Repeat from step 2 using the Dack's Duplicate token instead.

This loop turns the legend rule into an infinite engine by leveraging the global enchantment Leyline of Singularity, which ensures that every nonland permanent on the board is legendary—including clones. When you cast Dack's Duplicate and have it enter as a copy of Ratadrabik of Urborg, the presence of Leyline of Singularity immediately forces you to choose one to put into the graveyard due to the legend rule. As that copy dies, the original Ratadrabik of Urborg triggers to create a nonlegendary token copy of Dack's Duplicate, which itself enters as another copy of Ratadrabik of Urborg. Because this new token is also subjected to the legend rule by Leyline of Singularity, it dies immediately to repeat the process infinitely, forcing a draw and generating endless death, enter-the-battlefield, and leave-the-battlefield triggers.