I'm okay with most of this, but here are my thoughts on a few.

1. The fusion think is more like the energy goes into Taegen and his physcial form, which is his core, a stone around the size of a human heart, must be held by Taegaen while Ul is like this. This only lasts until Ul starts to enters adolescence, in which the core will begin to deteriorate. After a period of a few months, it'll be gone and he'll look like the picture.

2. Taegen doesn't have him trained, they just travel together based on a whim. They have a begrudging respect for each other, but they don't have a bond, which is why I left it out.

3. Divines have a bit of a chaos causing reputation, hence why they are called Divine Reapers. The last time one was seen, it cut a large swath of Terror, Destruction, and Death throughout the land. My plan was to have Ul fight against his own destructive instincts and urges. Also, having the Raiders face of against one would be interesting, a type of Grand Boss mob to fight. Just an idea for possible plots.