Cathedral of Sheoldred

When Cathedral of Sheoldred enters the battlefield, search your library for a card named "Sheoldred, Whispering One" and put it into your
hand
Cathedral of Sheoldred enters the battlefield
tapped
When Cathedral of Sheoldred is untapped, "Sheoldred, Whispering One" costs {1} less to cast
When Cathedral of Sheoldred is tapped, it doesn't untap during your next untap step
{t} add {b}{b} to your mana pool