Yenna, Redtooth Regent + Second Wind + Leyline of Singularity

Yenna, Redtooth Regent

Second Wind

Leyline of Singularity

How it works

1. Activate the mana-producing creature by tapping it, adding at least 2.
2. Activate Yenna by paying 2 and tapping it, creating a token copy of Second Wind attached to the mana-producing creature, then untapping Yenna and causing you to scry 2.
3. Put the oldest Second Wind into your graveyard due to the legend rule.
4. Activate the Second Wind token's second ability by tapping it, untapping the mana-producing creature.
5. Repeat.