When we're introduced to Tryston, he's arrogant and powerful. His magic is much stronger than Celyna's. He held himself as superior to everyone, even standing in judgment of Szandor and Xiuhcoatl at times. So, as you can imagine, Tryston and Zedekiah started off on less than friendly terms. But eventually they grew closer. Though he didn't want to, Zedekiah ended up having to be the one to let Tryston in on a lot of things: His past as a slave, Celyna's past as a slave, the conditions of the slave mines.
And each time, Tryston's sheltered view of the world shattered.
This is just one of many turning points in which we get to see the man Tryston grows into through Heir of Elendri. And it's one of my favorites because it shows him begin to accept his vulnerability.