Sacrificing a permanent is a high cost to pay, and Korvold, Fae-Cursed King makes you pay that cost every time you play him or attack with him. But that second ability more than makes up for it. Every time you sacrifice a permanent (whether to Korvold or not), you draw a card and Korvold gets bigger.
That ability makes Korvold into the ultimate payoff card for a sacrifice deck. Every fetch land, Treasure, Eldrazi Spawn and Clue you use draws you a card. Every time an opponent wipes the board while Viscera Seer or Ashnod's Altar is in play, you draw and scry for each creature you had. Some of those drawn cards will be token generators like Siege-Gang Commander or Mycoloth that make more sac fodder, drawing you more cards.
With all those cards, you can overwhelm your opponents in value. Or, you can keep growing Korvold with sacrifices and swing in for 21 commander damage in the air.
Jumbo Commander is a YouTube channel devoted to Magic: The Gathering, with a focus on Commander.
Connect: YouTube Twitter