PC on green focus plz

Chung's Focus
Energy +12 req. 9 energy storage
Health +45 while enchanted
Energy +15
Energy reg. -1

I've heard of builds using +12 +15 -1 focus' but have no idea what they are going for. Any help is appriciated.
~Mia

5-10k i think

maybe 15k

Thankyou!