Board Thread:General Discussion/@comment-31188206-20170201130302/@comment-28568301-20170204044013

What we do know is

1. Zahard is immortal and can't be killed inhabitants of the tower, that is his contract, except Irregular because they are free from them. We do know that 10 great families children are usually bound by special contracts since birth. It is nonsense for Zahard not to implement this to control them and instead says "Yeah they're my sons and i free you from all these contracts including my not-killed-by-resident-of-the-tower-contract, come kill me boy!" (If you try to say the contracts exception is his blood related children, thats fanfiction, cause there is no such information now)

2. Worst mistakes can mean many things. Perhaps since they have blood of Zahard, unofficial unlike the princess, and one of them is weak as hell except for his regeneration, they can be used to breed monsters (like the mad dogs) and cause distruptions to his rule. perhaps it is like what Athanos said, they are too weak to safeguard their parts of key.