They are the rarest and the true first printing of the cards
That means its fine for this deck out of the box and in a pod with other March of the Machine precons, but there are simply better options in almost any other circumstance That being said, Cavalry Chase does come with 10 Planechase planes, five of which are brand new
It's great in sacrifice decks that want a cheap creature to sacrifice and recur over and over, but midrange decks can also use it as a sticky threat that scales well into the late game thanks to kicker
As many times as you want, provided that you have enough energy counters to use the ability
1 Lord of the Accursed
When I upgraded my copy of the deck, I focused on the equipment theme, adding a few cards I had which played well with that, and removing some of the cards dedicated to making creature tokens, like Midnight Haunting or Spectral Procession