The Forgotten Goddess of the Tuatha Dé Danann

The Blackbird - Noir had inherited the same innate ability as Levi, he didn't know if it was due to his Dominance ability or due to the Black Wing of Lunacy which also had the same skill. Whatever the case, this had proven incredibly useful. 

Realizing this, Levi devised a plan, first, he would use Lunacy on the bird, then order it to use Lunacy back on him. This way, both of them constantly improved their ability and resistance to mental attacks.

But it wasn't as simple as Levi had hoped.

He vividly remembered the first time he fell under Lunacy's effect. It felt as though something foreign had invaded his mind, disrupting his thoughts and digging up his deepest emotions. He had nearly lost his sanity during that first attempt. 

In comparison, the blackbird handled it slightly better, only letting out some distressed caws under Lunacy's influence. 

Nevertheless, the practice had greatly benefited them both.