If you built a deck that hinges on playing a very specific, high mana card for some reason, you can't risk losing that key piece because you hit it with an early game impulse draw and didn't have the mana to cast it yet
The first will tap for and then put the top land on your library into your hand and the other cards into your graveyard and then trigger your background Commander
Quicksilver, Speedster The idea behind Quicksilver, Speedster is that you flash it in on someone's end step, smash with it on your turn, then have it tapped to keep the rest of your spells up at instant speed
2/2 white Fox with vigilance
Token decks that use white mana also have access to Halo Fountain, while artifact decks can use Mechanized Production, Knuckles the Echidna, or Hellkite Tyrant