There are many ways to get this achievement.
I was able to do it with Watcher as she has some easy ways to increase Energy.
Using Pure Water/Holy Water relics and Deus Ex Machina/Collect cards allows you to accumulate Miracle cards (they are retainable) that add 1 Energy each one.
If you manage to reach the Divinity by accumulating 10 Mantra, you get another 3 Energy upon exiting the stance next turn.
This means: your normal 3 Energy + 3 Energy after leaving Divinity + 3 Energy from Miracle cards = 9 Energy!