Oko, Seeker of Sparks

When Oko, Seeker of Sparks enters the battlefield, choose a color.
{t}: Search your library for a card of the chosen
color. If that card isn't a Planeswalker card,
discard it.
Threshold — As long as you have seven or
more cards in your graveyard of that color, Oko,
Seeker of Sparks has "At the beginning of your
upkeep, transform Oko, Seeker of Sparks."