Noble Mind

[Darkfaith]

What does this skill do?

[Andrew]

It raises your Empress Blessing skill. When you hit lv 120 on a KoC, you have default lv 24 Empress blessing.
Every 5 levels after 120, Neinhart will give you a quest to go talk to him to raise the Noble Mind skill level.
My Noble Mind is lv5 because my DW is lv145 (lv6 Noble Mind @ lv150). All my characters on my account currently level 29 Empress Blessing.
Hopefully that helps D:

[Endgame]

Basically, it's Empress' Blessing levels 25-30.

For revamped Cygnus Knights, just level to 150 to max it.

BWs, NWs, and Mihiles have to fight a nerfed version of Arkarium once a day to level it up though. (My 120 unfunded Mihile soloed him just fine. But there's no reason to even bother with Mihile anymore.)