The Kingdoms of Terror

One of the better ones of the entire series. This is the turning point of the series from the Kai to the Magnakai - or in other words, you're levelling up! The basic abilities from the first 5 books are now getting upgraded powers.

It's not just the mechanics are getting an upgrade, but also the lore. Lone Wolf is finally taking the battle to them as the hunt for the lorestones truly begins. You're thrust into civil unrest among the darklords, hence lots of flavour material, making for a really great read.