Creature cards in graveyards can't enter the battlefield.
Players can't cast spells from graveyards.
This hound is hell of an dog. Really powerful, if it would be printed as an mythic it would be fair enough for his abilities. CMC3 for vigilance, lifelink, menace and an included Grafdigger´s Cage with 3/3 is a huge impact on the board. Including: it will have an etched crosshairs for opponents removal spells.
Who's a good doggo ? That one for sure !