Ruxandra's Oath

When Ruxandra's Oath enters the battlefield,
each player exiles four cards of their library.
At the beginning of each end step, or whenever a
Planeswalker dies, you pay put a card from exile
into its owner's library and put a +1/+1, Flying,
Deathtouch, Hexproof, or Menacecounter on
target creature. They become Eldrazi.
"I can't "Watch". What you have done may not
last. With samples, I promise the Simic and I can
find out more."