The Divine Rolls augment text says, “At the start of every stage, including this one, gain 4 free rerolls + 1 for each of your Heavenly champions. Gain a Kha’Zix and a Malphite.”

Note that the extra rolls from Divine Rolls count for duplicate copies of the unit! In Liluo’s game below, he puts in 5 Heavenly units, three of which are unique. He got 9 rolls on Stage 3-1 = 4 free rerolls + 1 x 5.

Link to Clement’s original post for this tip