What is a mythic treasure?

So I got this flash pack offer pop up and there’s a “mythic treasure” in there, what exactly is a mythic treasure??

Sacred Treasure is used to level Delve Hoards.

It’s the highest rarity of treasure cards that are used to upgrade hoard level and quality of factions in Underworld

Additional help center stuff:

Other fun facts about Sacred Treasure:

  • You can level it and trait it, just like a troop!
  • No, there’s not really a good reason for it.
  • No, it’s not actually a very good troop.

They aren’t even affiliated with a kingdom, so you don’t get kingdom power or any of the other benefits.