I'm not 100% sure but I think it's related to the Azure sword clan killing the legendary beasts, specifically the Pheonix.
The person (forgot his name) who was hunting and killing all the legendary beasts was in the azure's clan and he seems to be stronger than him so he can't stay there to protect his phoenix and decided to go to the other clan while he could use them as a cover and grow stronger. from what i understand.
1. He wants to kill Bahal (the red hair guy from the Red Dragon clan he's in now), cuz He was one of the people from Arthia who betrayed his younger twin brother.
2. He needs to complete the special quest from the Void Dragon, who wanted Cain to kill Saber God (who is from the Azure sword clan).
3. Cain wants the cores of the Legendary Beats from Saber God.
4. He needs info about the Red Dragon and the Summer gueen (leader of the Red Dragon)
Now to explain... Cain wants to eliminate all people who were somewhat responsible for Jeong-woo's death. Jeong-woo was the leader of Arthia. The 8 strongest guilds of the Tower joined forces in order to eliminate Arthia and Jeong-woo, thus Cain wants to destroy not just the members of Arthia that betrayed his brother, but also the 8 Great clans. The Red Dragon clan happens to be one of the 8 clans. Also the Red Dragon clan is the strongest clan in the Tower. Going against them practically = death. Cain, at this time, is to weak to go against a whole clan or even a high ranker like Bahal. So Cain needs info - thus he infiltrated the Red Dragon. Thanks to Bahal being... well Bahal (confident, arrogant high ranker who beleivers he's unbeatable) Cain managed to earn Bahal's trust. So Bahal doesn't really expect Cain's potential betrayal.
Tysm for this, I've forgotten so much I can hardly remember who's who, let alone the people he needs to track down and kill
I'll shorten it for you... The people NOT TO KILL are:
- Cain's friends (somewhat): Edora, Phante, Kahn, Doyle, Yul,
- Cain's masters: Nayu (the Martial King), Henova (the Blacksmith), Galliard (the Black elf)
- And OneHorn tribe
Others that the mentioned above (and some people Cain will encounter in the future) are on his Death list or disposable...
Hahah too easy! Yeah it's seems a lot simpler to mention who he won't kill haha, the list is short, sweet, and easy to understand. I'll probably end up thanking you 100 times today because I love this manga but too lazy to read through it again to remember the lore
my dumb ass can't comprehend so will someone please explain whys he on the enemy side,, again?