Demon invasion.

I have 6.5 in-game months played. Knowing that Vitya becomes more active after capturing 1 blue Castle, I haven't touched any of them yet, although I could have captured 5 already. There's a trick: when looting the treasure vaults of Mages or Dragons, you get one random Dragon artifact. I found a piece of armor, completed the set, and gave it to the main Castle. Besides the complete set, I have 2 crowns, 1 ring, 1 pair of boots, and 1 cloak. I can assemble a second set. The treasure vaults of Mages and Dragons are on my territory, and my hero moves quickly with 2 pairs of boots. What's your problem with doing raids on the Library's guards using only Imps? You can reduce their numbers that way. The Necromancer's cloak and ring, along with the Spirit, will help you fight to the last. For example, the Mentor's guard was reduced to a size where it's "good for gaining experience" after just two raids; you can spend more time on the Library. (The guard is very powerful - http://c2n.me/3PNWwBd - but I think it's passable). I haven't found the way to it yet, and I don't have the Tears either; there's also one more obelisk somewhere. Maybe I'll get lucky and be able to assemble a second Dragon set by that time