Arcbound Reclaimer + Showdown of the Skalds + Dark Sphere + Madame Web, Clairvoyant

Arcbound Reclaimer

Showdown of the Skalds

Dark Sphere

Madame Web, Clairvoyant

How it works

1. Cast Dark Sphere either from your hand or from the top of your library by paying 0
2. Showdown of the Skalds triggers, putting a +1/+1 counter on Arcbound Reclaimer.
3. Activate Dark Sphere by tapping and sacrificing it.
4. Activate Arcbound Reclaimer by removing a +1/+1 counter from it, putting Dark Sphere from your graveyard onto the top of your library.
5. Repeat.

This clever loop centers around Madame Web, Clairvoyant, whose static ability allows you to cast noncreature spells directly from the top of your library while you look ahead with her top-deck awareness. You initiate the engine by casting Dark Sphere for zero mana, which triggers Showdown of the Skalds's later chapters to place a +1/+1 counter on Arcbound Reclaimer. You then sacrifice Dark Sphere to reduce incoming damage, and spend that very counter using Arcbound Reclaimer's activated ability to recycle Dark Sphere right back onto the top of your library. Because Madame Web lets you cast it again immediately from the top, you can repeat this cycle endlessly to generate infinite storm count, artifact leaves-the-battlefield triggers, and enters-the-battlefield triggers.