You know what’s crazy? Shadowhand Essek Thelyss could have just been the Mighty Nein’s interrogator/jailer in the Dungeon of Penance. And if they’d escaped, who’s to say he wouldn’t have continued to hunt them down, to silence them for what they knew? He could have been a boss fight and nothing more.
Instead, because the Nein gave him cupcakes and invited him to dinner, because they took a personal interest, he’s at their side casting support spells and using his dope gravity magic to help take down Aeorian monsters.
He’s the key to unlocking any of the beacon/dunamancy lore they’re encountering. Without Essek’s tutelage, Caleb’s knowledge of dunamancy could have been limited to only a few passing mentions in books. Instead he understands it well enough to reverse-engineer some of the spellcasting. And when they encounter ancient experimentation with the arcane applications of dunamis, they have the most knowledgeable person on the subject in Wildemount there in the room with them.
Essek’s presence in Eiselcross is a huge reward to the Nein for the efforts they made with him, and it serves two purposes: 1) a powerful ally against Lucien & the Somnovum, and 2) access to all the beacon lore present in Aeor to be discovered. They could have missed all of it, or at the very least still encountered it but not understood what they were seeing to the same extent.
I just sit back and think about all that sometimes.