Runes allow you to upgrade your Heroes.
This system will launch in 2018.
Why is Runes not available from launch?
The Rune system is designed for experienced players, and adds another level of strategy on top of the game. While the game is new, and the team is still balancing the early stages and adding new Heroes and Skills, adding Runes adds a level of complication which could make it more difficult to balance the game, particularly as we don't yet know how players will play, particularly in the PVP modes. So we decided to remove it from the launch version of the game.
Once the game has been launched for a while, and we are happy with the balancing, we will launch the Runes system.