Dannanth, the Lawmaker

Flying, Vigilance
This creature's power is equal to the number of nonland permanents with unique color pairs
among cards you control.
Domain—{9}: Reveal cards from the top of your Library, until you reveal a nonland permanent
with a color pair you don't control, you may cast
that card without paying its mana cost. This ability
costs {x} less to activate for each basic land type
among lands you control.