Unlock it!
The first thought that came up to Isiah's mind was that he transmigrated into a different place now that he was looking into the void after the disappearance of his parents' corps, he then realized that the only thing that came with him was the mysterious grimoire he found in the basement of his old house.
Something clicked inside of him, it was not a coincidence, then with the idea of the triggering element of emotions to his magic, he came up with a wild theory that seemed more realistic in his mind.
Emotions are key to activating his magic, he doesn't seem to know how to do it unless he is angry or very sad or confused or all of them.
His emotions are the link between all the incidents of him using his magic, the times when he forced himself to do it like everyone else he couldn't or made a joke out of himself.
Isiah held the grimoire with two hands and then started to look at it from above.