Dura's Tears are consumable items that can only be used in the Arcane Labyrinth.
"A miraculous elixir that has the ability to fully restore heroes' life and energy. However, it would seem this elixir only works in the Arcane Labyrinth."
Using a Dura's Tear will revive all your fallen heroes, restore hit points of wounded ones, as well as all heroes' energy to 100%. Each one is single-use only. By completing your weekly quest you can obtain up to 3 Dura's Tears each week.
Players should not be tempted to save Dura's Tears for later use, because potential gains from completing the Labyrinth outweigh the value of 1 or even 2 Tears. Keeping that in mind, do not hesitate to use them if only they will allow you to complete the Labyrinth.