Yanael, Alzara, and Soara were a little hesitant about donating blood to a mysterious egg that didn't even belong to Zach, their master. But it did belong to his sister, who he was close with. And Zach was clearly eager to help her, though that wasn't strictly why he did it.
Yanael, Alzara, and Soara were all familiar with Zach's attitude when it came to summoning. He was curious. He wanted to see and know more.
He didn't go around experimenting with others' familiars, but he did go around and ask both the familiars and their masters questions about all kinds of things. Whenever he had some free time and wasn't too tired, he asked the library pixie for the latest on all things summoning and familiar-related.
He had to ask for the latest since he had already gone through everything interesting and relevant to his desires.
That was why he could formulate a hypothesis about the workings of Lexi's egg.
