Oath of all

This card costs {2} less to cast for each
planeswalker you control and {1} more for each
eldrazi on the battlefield.
Choose a colour or type. All cards of that colour
or type cost {0}. you may cast cards of that colour
or type from outside the game.
Tap all planeswalkers you control: untap all non planeswalker permanents you control
I will keep watch, I will keep watch, I will keep
watch, I will keep watch, I will keep watch, I will
keep watch...