KMST 1.2.455 - Moar changes

All adventures from my understanding need to unlock their goddamn skills, no? Then you have horntail, who unless it changed, but the fact it was at one point ridiculous, is the only monster in the game that drops/dropped zerk 30.

As far as I can recall, only Heros, Paladins, Bishops, Arans, Evans and DBs need skillbooks from Zak/Hilla. The skillbook drop rate from Zakum has been lowered to nonexistent when it became instanced, for no reason I can see. So it's pretty much only Hilla.
As for Horntail - like almost all other monsters, it doesn't drop specific mastery books anymore. It drops Mystery Mastery Books. You have equal chance of getting Zerk 30 from an MMB purchased in FM off a botter, as from an MMB HT dropped for you.