The Wheeling Runner - Unknown Event

You may spend any type of mana to cast cards that didn't start in your deck.

Whenever The Wheeling Runner deals combat damage to a player, you may discard your hand. If you do, choose four Vintage-legal cards at random. Add those cards to your hand. (The "Random Card" feature on a search site may help.)

Ready to run (You can have two commanders if both have ready to run.)