And its not wrong to use just Driven on a turn and Despair on another depending on the board
Its probably best to cast this at the beginning of combat or after attackers have been declared, before blockers are declared
Horobi, Death's Wail Horobi, Death's Wail turns Retribution of the Ancients, Shadow Alley Denizen, Squee's Toy, and a bunch of otherwise unplayable cards into machine guns
As is always the case, only time will tell whether Decree of Silence will continue to rise or crash back down to earth
In the late game, for three mana, you can cast a creature that gains a +1/+1 counter for each creature in your graveyard, which in a Zombie deck is usually a lot, on top of also getting the 2/2 Zombie for each creature you cast