I may be new, but I like it. Sure there's a lot of back story and not as much in the present, but the malleability of this villain is impressive:
Depending on how I want to use him, I could have him as the stock one shot "crazy evil druid" for a hack 'n slash night of fun.
I can have him (as it implies to me) be the intelligent, calculating (albeit, still crazy) plotter where you really don't want his focus on you, the hero. This version of the villain could be a series of adventures or just a recurring thorn in a hero's side. (Dating myself, but thinking of the Swamp Thing comics in the late 80s early 90s where he went for revenge on tons of people).
I could have the religious fanatic with all the lizardfolk (and other) followers where killing him would only martyr him, so what are the PCs to do?
I could go the tragic anti-hero route and have the PCs have to figure out how far gone this guy is on whether he can be "brought back" or not and if he can, how will that play with the cities and towns he's been attacking.
Maybe somehow, combine all the different elements for a total campaign villain? (Okay, that may be stretching it a bit)
It's all in there, just where you want to focus. As it is written here, I really like this character because I can use him in various ways for my own stories. If the rules were for a villain to then use in a specific adventure, then there's not enough here. I see the rules about the adventure OR campaign sourcebook with a big "OR" there. As written, this would fit nicely in a campaign sourcebook.
As a villain that I can take and own for my adventure writing, this is pretty interesting.