It was not that Mike had not fought with Ragnaros before. It was just that Ragnaros has used this move once.
However, the last time he used it, the sky was covered with dark clouds, but it did not seem to be as strong as it was now.
The best proof was that after the battle ended, and when Mike went elsewhere, he did not hear anyone talking about the dark clouds in the sky anymore.
Now, after Mike had used the Space Travel Bracelet to move from Sarco City to the Volk Plains, he could still see the dark clouds in the sky.
This was enough to explain how dire the situation was.
It was very likely that the entire second world continent had already been covered by the dark clouds.
Mike looked at the dark clouds in the sky and did not want to waste too much time.
He was not sure if his strength was enough to defeat Ragnaros. After all, he was currently in a weakened state, and his opponent had added the restriction of using 50% of his strength.