Blackhart Signet Ring

Blackhart Signet Ring enters the battlefield tapped.
{t}: Add {u}, {b} or {r} to your mana pool.
{t}, Sacrifice Emblem of Sunwatch : Fateseal 2. (To fateseal 2, look at the top two cards of an opponent's library, then put any number of them on the bottom of that player's library and the rest on top in any order.)