* The Oct 11th, 2016 patch has fixed this achievement! *
For this achievement, you have to Enchant/level up a Rune card to level 4.
On the main menu, select Deck, and then Temple.
From here, press A to Mediate and gain Runes and materials. When all the slots are full, press X to process them.
You will see a screen saying 'Congratulations!', which tells you what you've acquired.
From here, back out of the Temple and go into Enchant Rune.
Choose a Rune to upgrade, press Y to Choose Materials, choose all the Runes that you want to use for the upgrade/Enchantment. When you've finished, press B and you'll see a summary screen of what you'll be using, and the Coin cost.
Press LT to Enchant, and repeat this whole process, until you have met the level 4 requirement, and the achievement will pop.
Doing this can also net you the following achievement, when you acquire 5 grey Runes in a row. :)