Shyian, Eternies Invoker

Vigilance, Planeswalker convoke (Your planeswalker
can help cast this spell. Each planewalker you can -1
a loyalty counter while casting this spell pays for 1 or
one mana of that creature's color.)
Planeswalker Cascade(When you cast this spell, exile
cards from the top of your library until you exile a planeswalker card that costs less. You may cast it
without paying its mana cost. Put the exiled cards on
the bottom of your library in a random order.)