Grim Demon knew that it was time for him to choose a side, but he didn't feel too conflicted. He chose to stand on Zhou Wen's side.
Guardians weren't pure dimensional creatures. They were just tools created by dimensional creatures. He had no feelings for them.
Of course, this wasn't the reason he chose Zhou Wen. It was mainly because Demonic Neonate was Zhou Wen's Companion Beast. Demonic Neonate was definitely on Zhou Wen's side, so Grim Demon had no choice. He would choose whichever side Demonic Neonate stood.
It wasn't difficult to choose a side. The difficult part was how to make the stand.
Grim Demon knew that Zhou Wen didn't trust him, and Demonic Neonate listened to Zhou Wen. Therefore, Grim Demon felt that this was a very good opportunity. If he did well and obtained Zhou Wen's trust, he might be able to escape the awkward position of being "reserve rations."