Closing all 6 Hel Tears is required to complete the favor "Hel to Pay". Closing the first two will happen automatically as they are the main mission objectives and cannot be missed. The favor "Hel to Pay" will appear in your journal after closing the second of the tears.
After closing each of the Hel Tears, you will receive one Frozen Spark and some other resources such as Essence of Hel or Dust of Realms, and some Hacksilver (The number of resources and hacksilver depends on the order, increasing as more tears are closed). When you collect all 6 sparks then they will turn into Frozen Flame, an item that will allow you to upgrade your axe.
