Rex, Cyber-Hound + Trench Behemoth + Llanowar Scout

Rex, Cyber-Hound

Trench Behemoth

Llanowar Scout

How it works

1. Activate Rex using Llanowar Scout's ability by tapping it, putting a land from your hand onto the battlefield.
2. If the land is mana-producing and enters the battlefield untapped, you may activate it by tapping it, adding at least 1.
3. Activate Rex using Trench Behemoth's ability by returning the land from the battlefield to your hand, untapping Rex.
4. Repeat.

This clever concoction turns Rex, Cyber-Hound into a one-dog recursion engine by feeding on activated abilities exiled into its memory banks. Once Rex has absorbed the text of Llanowar Scout, you can tap Rex to rapidly dump lands onto the battlefield, triggering your landfall effects. To untap Rex and keep the loop spinning, you also need Rex to inherit the ability of Trench Behemoth, letting you bounce those same lands right back to your hand at a moment's notice.