In short, Leo Ray's invitation to both was undoubtedly in the interest of all three parties, so Grey Elder and Yonir naturally had no reason to refuse.
Upon arriving at Ice Stone City and entering the battlefield area, both were surprised but became increasingly aware.
Just as Leo Ray mentioned, the true mastermind behind the Black Abyss Brotherhood was becoming clearer, and it was very likely the Temple of Light before them.
However, even though they were seventy to eighty percent sure, they still did not choose to act immediately.
Firstly, because the Temple of Light had not yet revealed a real flaw, and if they attacked the wrong target and allowed the other side to benefit, the Human World might be beyond saving.
Secondly, while both keenly sensed a strange and mysterious power stirring within the city, that power was still in an early stage, so they chose to continue observing rather than act rashly.
