Please explain me how is this possible? Whatever differences Altruis had with Illidan, you don't just ask to a random dude that you meet for the first time to go and kill your former allies and brothers. Just because you think that they were corrupted. Exactly, he THOUGHT that they were corrupted so yeah, hey guys, go and kill them because they are becoming more demons than hunters, just because I say so.
But he was sooo wrong. We learn in Legion the fate of Varedis's soul, Illidan's best student that Altruis asks you to kill because ''he was gaining so much power he must be destroyed!!.
His demonic soul went to the Twisting Nether where he was found by Kil'jaeden. Kil'jaeden heaped endless torment upon Varedis, who resisted for a time, but it was not pain that broke his spirit. The Deceiver played upon his shock from the battle at the Black Temple. Champions had been prepared to face Varedis and known to use the Book of Fel Names, so who had told them of that power? Varedis knew it would not have been the Burning Legion or the Shadow Council, as they would have preferred the book to remain intact. Kil'jaeden convinced Varedis that it could only have been the Illidari, who knew of his power and betrayed him. Varedis surrendered to the demon within him, forsaking his mortality. In the process, he and his glaives were infused with great power by Kil'jaeden's eredar allies.
Can you see it now? Varedi's tried to ressist to Kil'jaeden's torment. How can someone that is CORRUPTED according to Altruis, would resist such torment for so much, ONLY to surrender because he found out that it was one of his former BROTHERS that betrayed him...
And guess what, every single demon hunter teacher that Altruis asked you to kill (including Varedis) is back in Broken Shore as the Burning Legion's servants. Great plan Altruis, great plan indeed.
If someone has read the book like I have will agree that Illidan has literally done almost nothing wrong. I say almost, he is obviously not perfect. So how can someone pick Altruis? Kayn is the ONLY option. A true loyal soldier to Illidan. Someone that will not backstab you just because he doesn't agree with your methods, or because you are becoming more powerful to slay demons. (which is the purpose of demon hunters in the first place....)
The only reason I ever thought to pick Altruis was because of Akama. But fuck this, I just can't trust and follow this guy.