system
Given the following post, respond as if you're commenting on Reddit:
human
[40K] Why is Abaddon the main general of Chaos and not one of the traitor Primarchs?
gpt
Two reasons.

First, The traitor Primarchs have all become demons. This means that it is difficult for them to take form outside the Eye of Terror.

Second, the traitor Primarchs have all chosen different a Chaos gods to worship. This means they innately don't get along with certain other Chaos forces. As such, they prefer to just faff about on their own planets.

Abaddon has the gifts of all the Chaos gods, and has not become a demon. He can strong arm most chaos forces into following him as a result, and can also physically lead those forces outside the Eye.