Right, so there have been a lot of queries on how Viserys is a skinchanger, what his abilities are, and so an and so forth. I'll lay it out as clearly as I can.

Viserys is half Blackwood, due to Betha Blackwood being his great-grandmother. She was married to Aegon V, Jaehaerys II and Shaera were her children, Viserys's grandparents, who are thusly half Blackwood. They did incest, and so did their own children, Aerys II and Rhaella Targaryen.

Therefore, Viserys is also half Blackwood in the modern day.

No, Valyrians were never Skinchangers. That's canon, and I'm not modifying or retconning it for this fic. Viserys's Skinchanging abilities explicitly has nothing to do with his Dragonlord blood. They are wholly separate, and are inherited from different ancestors.

There has never been a Dragonlord who was also a Skinchanger. I'd imagine that such a combination would be potent indeed, beyond anything the Valyrians ever did as Dragonriders.

The closest the Targaryens ever came to that was Bloodraven, who was half Blackwood, but lacked a dragon to warg into.

Will Viserys get a dragon?

That is for me to know and you, my dear readers, to find out. But who knows? It's certainly a strong possibility.

Why is Viserys a skinchanger when he explicitly was not so in canon?

Purely because of the SI. As the books established, there are several bloodlines with the potential to have Skinchangers. Not every generation has Skinchangers, and even then not everyone in that lucky generation might possess the talent. Bloodraven's own sisters, Mya and Gwenys Rivers, his full siblings and daughters of King Aegon IV Targaryen and Lady Melissa Blackwood, show no evidence that they had any of the gift.

Conversely, you also get freak cases like the Starks, who have married into several magic rich bloodlines like that of the Marsh King and Warg Kings, and spontaneously all of Lyanna and Ned's children are Skinchangers, with the talent skipping several generations.

Taking all this into account, it seems evident that every person of these select bloodlines, (which also includes several Wildling clans, as canon also showed, Blood of the First Men for the win, lol) even if not a skinchanger, has the potential to be one, dormant in them, and it can later be inherited by their descendants who might express the gift in its entirety.

Thusly, the SI dropping into Viserys's body has altered his metaphysical makeup, magically speaking. It's not the same mind which occupies the body, and in that shakeup, some things which were mouldering away in dormancy, have risen to the fore. That being, primarily, skinchanging.

Is Viserys going to be a Greenseer on Bloodraven or Bran Stark's level?

While Viserys would certainly, in the natural course of things, reach the level of power Bloodraven possessed as a warg before he went North and became a talking tree, becoming that powerful has a cost.

Definitely not. It seems quite clear that Greenseers are the mightiest of all Skinchangers, with the books explicitly stating, "Only one in a thousand is born a skinchanger and only one skinchanger in a thousand is born a greenseer.[10]"

However, ascending past the rank of a skinchanger to becoming a Greenseer is intrinsically tied to sacrifice- sacrifices that both Bloodraven and Bran paid to ascend to a higher level of power.

Viserys seriously isn't willing to do anything of that sort. So while he could become a Greenseer, with the strength of his bloodlines, he currently has no plans to begin maiming himself or attach himself to a tree.

How did Viserys force two men to commit suicide, and what does that have to do with skinchanging?

Varamyr Six Skins, a powerful and accomplished warg, attempted to possess a human, a female Wildling, and while he didn't succeed, he caused exactly the same thing to her, which Viserys did to his own treacherous servants in this chapter. She tore out her own eyes, carved bloody furrows in her face, bit out her own tongue, and died choking on her blood. This is canon, since it's far harder to possess a human than it is to possess an animal, which was pointed out in the chapter also.

Not a nice way to go, yeesh. Look up Varamyr Six Skins on AWOIAF or the books if you like.

What do Viserys's eyes flashing red mean?

It means that he holds the potential to ascend to becoming a Greenseer, and is not just any ordinary Skinchanger. Whether he chooses to do so is another question. This is also canon from the books, stating, "While most children has golden eyes, the eyes of greenseers are red or green. It is also known that humans can be born greenseers just as they are born wargs.[10]"