Once he is on the field, he will be incredibly lethal given he gets +1 to Power and Life for every creature that leaves the Graveyardwhich we already established, you will do a lot of
Return each card chosen this way to the battlefield under your control
Oh, and did I mention that if you draw three cards, lose two cards, and have a Psychatog on the table, you've just grown your 'Tog by +6/+6 (two cards in graveyard + Fact or Fiction + 3 cards in hand -- discard the three cards to have six in the grave, remove all six to give another +3/+3)
Managing to pull a mint gem-condition Alpha Black Lotus - autographed or not - is akin to winning the lottery
Treasures, Foods, and any other token that you sacrifice to activate also makes Korvold, Fae-Cursed King stronger
All around, Pua is a surprisingly good card