Instead of directly stopping creatures from attacking you, it forces your opponents to make a tough choiceeither pay they 3 mana for each attacking creature, or they let you create a 3/3 Ogre token for each one
For example, if you return two cards from your graveyard to your hand, discard one of them, then exile that card from your graveyard, you can activate Bonecache Overseer's ability that turn
The card saw plenty of play in its Standard format, and it's a strong addition to any deck with a cast from exile theme
In this example, sacrifice both Young Wolf and Woodfall Primus to Ashnod's Altar, which return to the battlefield with a +1/+1 counter due to undying and a -1/-1 counter due to persist, and you generate 4 mana
Thats how people interpreted and explained the card on our Discord when it got previewed