Clashing attributes like ice and fire was a dangerous game. No matter the situation, ice and fire could never exist in harmony. Having a little distance in between was still acceptable but to coexist in one host was practically impossible.
Each person present was a villainous expert and quite well-informed. They had never seen someone force two clashing attributes onto the same pet beast.
In fact, beasts of clashing attributes did exist.
However, those were born with it, an innate gift. Hence, the polarity was acceptable. But such pet beasts were usually worthless. No one would form blood pacts with them nor waste effort on trying to nurture them.
Furthermore, no matter human or beast, those with clashing attributes usually attracted disasters and had short life spans.