The Rune Store is open and functional!
While it may need some visual updates, I wanted to get the functionality in game ASAP to give players longer-term unlockables to work towards.
Runes can be bought and equipped prior to making a run, and once purchased, they will be available for subsequent playthroughs for all eternity.
They range from small damage bonuses, all the way up to unlocking every single skill for a class making him or her a killing machine.
They might make enemies drop more XP, or they might just make twice as many enemies spawn, but in a much weaker form so you can cause absolute mayhem.
Have fun!