Aries had a plan, and that was to trap Maximus in Maleficent's world. For her plans to happen, she needed to make them appear as realistic as possible. Hence, Abel, together with almost everyone, entered that spirit world and entrusted their lives to her.
They knew the risk — every single one of them was aware of it. But they still did. The witches and the night council deemed it the most efficient way to deal with a person like Maximus. And thus, they lent their powers to assist Aries. As they did so, Abel, Conan, and the rest were tasked to distract Maximus.
However, what they didn't expect was the amount of power and control Maleficent had. It wasn't like they underestimated it, but rather, they didn't think that Maleficent not only bring this strong repugnance against powerful vampires like the Grimsbanne and the Royal Family in the mainland but also, the power carried along the original Maleficent's will and twisted beliefs before she passed away.
