Okay, it's a little concerning why Martha reacted as if she'd sinned; it's not like he would eat her alive for climbing the power gap, which is a normal thing.
Apart from that, it seems more like an excuse. Besides, other people wouldn't inquire about his characteristics.
So, why did Martha run away? Onver sat on the bed, pondering all this, then shrugged, leaving Martha's behaviour as it was, and started thinking about assimilation.
In assimilation, one absorbs the blood of a beast or any compatible creature. There are issues with Martha's excuse. First, Alen would likely ask what type of beast blood he used.
"Well, it's not that large of an issue anyway. I wanted to assimilate even if the situation wasn't like this."
Now, there's a question of how Onver will do it without the blood of a compatible beast. Compatibility means a similar relationship in personality. A series of these things...
