Anyone know how to complete this one xD?

"Get to know someone" means - you have to obtain the knowledge on certain NPC.

In this particular quest you have to obtain knowledge on Freharau. To do this, raise your amity with him up to 300pts.

I got his amity up to 300, and spent 25 energy on his "First Awakening" knowledge. That gave me a +1 damage reduction buff, but the quest isn't completed for me. What am I missing?

Just confirmed that this quest DOESN'T work. At 301 amity with Freharau an option "First Awakening" appears in the conversation.
It costs 25 energy points and give you a buff.

And since he talked about the black power this is clearly the buff the quests is about getting and knowing.

.

Seems that they already fixed it. Just get 300 amity with Freharau and ask for knowledge for 25 energy