Q:For the longest time my friends and I thought that you couldn't regenerate something that was sacrificed, but then I saw the creature Augur of Skulls. So how does it work?
You can’t Regenerate sacrificed permanents. Regenerate says “Next time I would be destroyed, instead - tap me, remove all damage from me, and remove me from combat.” Sacrifice simply says “Put me from the battlefield to the graveyard (I die).”
Sacrificed creatures can’t regenerate because they’re not being destroyed.
The way Augur of Skulls works is like this:
You can pay (1B) for the first ability to put a Regenerate shield on it.
You can sacrifice him to make a player discard two cards, at the beginning of your upkeep.
While you can do both (pay 1B for regenerate, and then sac him), it’s not practical since Regenerate won’t save him from the graveyard.