Suspicious Cart

Hideaway (This artifact enters the battlefield tapped.
When it does, look at the top four cards of your library,
exile one of them face down, then put the rest on the
bottom of your library.)
{t}: Add {1} to your mana pool.
Whenever two or more creatures you control
become blocked you may sacrifice Suspicious
Cart. If you do, put the exiled card onto the battlefield tapped and attacking if its a creature.