Urza, Lord High Artificer + Corridor Monitor + Banishing Knack + Herald's Horn

Urza, Lord High Artificer

Corridor Monitor

Banishing Knack

Herald's Horn

How it works

1. Cast Banishing Knack by paying , targeting a creature you control that doesn't have summoning sickness.
2. Cast Corridor Monitor by paying due to Herald's Horn.
3. When Corridor Monitor enters, it triggers, untapping the creature targeted by Banishing Knack.
4. Activate Urza's first ability by tapping Corridor Monitor, adding .
5. Activate the creature targeted by Banishing Knack by tapping it, returning Corridor Monitor from the battlefield to your hand.
6. Repeat from step 2.