mtg commander double faced cards Treasure // Stoneforged Blade Double-Sided Token [Commander Masters To Tetzin, Gnome Champion Rapid Commander

Most of the likely zero drop spells do fall into that range, but there's a handful of possibilities like Everflowing Chalice and Zuran Orb that I could see showing up but aren't huge powerhouses

Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the new token will work

This is like having a Doubling Season or Parallel Lives right in the Command Zone, which is an intense amount of power at your fingertips right at the start of the game

It doesn't matter what happens to the Bird, Frog, Otter, or Rat that turn after it enters

The Showdown can be cast for 6, but the fact that its a modal card makes it so, so much better