Five mana grants you a typical edict creature stapled to an 11/11, assuming each player sacrifices a creature, and it only gets better
For example, cards like Senseis Divining Top or Realmwalker really benefit from changing the top card of your library Graveyard Once you have sacrificed your fetch land, assuming there are no replacement effects, they will end up in your graveyard
As long as the number of card types outnumbers the listed amount on the card, youll get an effect, so youll be wanting to discard, surveil, manifest dread, self-mill, and sacrifice as much as possible to get those numbers up
The planeswalker slotted into Mono-Black control and Golgari Control within the Standard format
People were playing around with Eldrazi ever since BfZ came out (and the deck was already impressive then)