[On Play] Look at 4 cards from the top of your deck
If your starting deck follows that rule, then the creature can serve as your chosen companion." The Wiki goes on to explain how you can only have one companion in a game, it starts outside the game, and counts towards your sideboard size (i.e., in Constructed play it is one of the fifteen cards in your sideboard)
Yep, more expensive, not less
If two nonland cards that share a color were milled this way, repeat this process
Eternalize (, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Human Shaman with no mana cost
These spells all have the new keyword tiered