@PKMNB0YI just found out about Angra mainyu's materials from book III, turns out end of four nights actually does exist and it is a really good skill.
Seen hereWith end of four nights, murderous intent can be used up until the last possible moment, meaning angra will get stronger and stronger over the course of the fight. Meaning! Angra Mainyu can actually be a servant on the calibur of Arash, but more of a glass cannon.
Thus, Angra Mainyu would likely fall under a similar role to his role in Atraxia, where his master takes the aggressive role (with a powerful magic like Fragrach) while he takes the supportive role. It makes a fun dynamic.
Just thought you'd like to see this. I found this pretty cool in all honesty