<p>The first thing to do is acknowledge the great age of the staff and zerstorer. They have both been around long enough to amass prophesies and legend relating to them. As zerstorer is otherworldly and the original wielder of the staff, it stands that the staff must be otherworldly. In fact, it is the staff that allows him to travel the worlds. Additinally, as there is a sort of wesen home world, it stands to reason that all of the supernatural forces are likely to originate outside of our world. Hexenbiests are able to slow the aging process as Henrietta confirms, and we know she is much weaker than eve who is much weaker than zerstorer. It seems plausible that he could have been around for tens of thousands of years and have lost the staff at some point, possibly due to enemy grimms. The staff was broken up on our world, but it was reassembled and brought to the mirror world so we know it can exist in other worlds. Additionally, as the power of the staff seems to be an attribute of the wood retained even when broken, it stands to reason that there is a source material and potentially other staves as well. We know grimms can mutate a little because of their strange interactions with cracher-mortels, musai, and jiamuru xiunte. The staff, as you said, has powers like the hexenbiest Diana, and as Nick is able to wield that same power in a more passive manner, it suggests a relation between the three species. The wesen in the mirror world understood Nick was a grimm I believe, so that would indicate that grimms did not originate on our world. More likely, the followed zerstorer as he set out to conquer, and their reputation as wesen killers is the result of this effort since wesen serve zerstorer. As for him being a hybrid, this is unlikely. His dependence on the staff suggests it is the heart of his power not an additional source. If he were just a hybrid his abilities would be independent. As you said, hexenbiests corrupt their hosts. The staff does too as it had an obvious obsessive effect on nick and zerstorer. So if we consider the staff as the source of the corruption, it is its vestigial power in hexenbiests that is corrupting them. Notice that the much weaker adalind was more in control of herself than the powerful juliette, suggesting a possible correlation between the quantity of power and the corruption. Also, grimms and hexenbiests have a seemingly insurmountable aversion to one another as Nick and Juliette were unable to make their relationship work. Given this aversion it is still possible but very unlikely zerstorer is a hybrid, especially as this would potentially dilute the zauberbiest power or outright cleanse it with the grimm blood.
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Consider grimms to be a blank template. Introduced to magical power they become zerstorer, and over the generations diminish into the weaker hexenbiests. Exposed to animals, possibly with this power as a catalyst, the become the more common wesen. All of the species are related, but it may be that grimm lack the transformation because there is no outside material contributing to their power. As nick gains experience with other wesen, he develops additional abilities so we know this is a quality of their species. Basically, grimms are like evee from Pokémon and different stressors provoke different transformations.
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As far a Diana’s vision, we can’t really link that to her royal blood as the royals have not demonstrated any real power beyond the financial and political. We would have seen them woge in one of the many fights if they were able to do so. He vision is tied to the same energy as the staff and other hexenbiests which is why it triggers specifically in relation to these things.
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