Lex put up a tough front during negotiations, and at the same time inquired about the rites of passage. But in truth, he did not care too much. The rites of passage were interesting, and Lex would have gone through it just to see what the experience was like.
But mostly, his mind was on the Glyph. When he got time, he would learn more Glyphs and practice them to see what the results were like. Moreover, if his theory was correct where fairies could just replicate special techniques or abilities that were unique to various races because they had all affinities, then fairies would be over powered to a whole other level.
In fact, they might even be the most impressive race he had met yet. In that case, he was 100% sure that there was something else holding back their growth than just a curse that made them more likely to be enslaved.
It was something he needed to figure out, since he had no intention of staying weak.
If anyone is interested, the castle blueprint and chamber rewards were given in chapter 714 if you want to go back and read.