Ugin saw the gem that connected Bolas to his Meditation Realm as the key to his brother's downfall.

Finale of Revelation

Draw X cards. If X is 10 or more, instead shuffle your graveyard into your library, draw X cards, untap up to five lands, and you have no maximum hand size for the rest of the game.
Exile Finale of Revelation.

"Brother, your fate has always been bound to mine. Now we have reached the place where they shall both end."

Foundations