In 80s Trigon met Arella again after her escape. He didn't kill her and said; “I still have several years, need of her". It is not explained what Trigon meant with his words.
But in the 2014 Arella explained Trigon's words and said crying; “Trigon once said he still wants me, for several years. I don't know what he meant, hard to understand Trigon. But he didn't try to kill me. I think he sees me as something he wants to own forever. It's kind of an obsession. Trigon is emotionally unstable.”