Arthur, Marigold Knight + Preston, the Vanisher + Scroll Rack + Felidar Guardian

Arthur, Marigold Knight

Preston, the Vanisher

Scroll Rack

Felidar Guardian

How it works

1. Activate Scroll Rack by paying 1 and tapping it, exiling Felidar Guardian from your hand face down, then putting the top card of your library into your hand and putting Felidar Guardian onto the top of your library.
2. Declare Arthur and another creature as attackers, triggering Arthur, looking at the top six cards of your library and putting Felidar Guardian onto the battlefield tapped and attacking.
3. When Felidar Guardian enters, it and Preston trigger.
4. Resolve the Felidar Guardian trigger, blinking another permanent you control.
5. Resolve the Preston trigger, creating a token copy of Felidar Guardian that is a 0/1 Illusion.
6. When the Felidar Guardian token enters the battlefield, it triggers, blinking the nontoken Felidar Guardian.
7. Repeat from step 3.

This clever loop centers around Arthur, Marigold Knight, whose attack trigger dives deep into your library to pull out Felidar Guardian without casting it. Because Felidar Guardian entered the battlefield uncast, Preston, the Vanisher swoops in to create a token copy of it, which immediately triggers its own blinking ability to reset the loop. Meanwhile, Scroll Rack acts as your setup engine, ensuring Felidar Guardian rests neatly on top of your library right before you declare attackers.