No, each X-rank monster is unique. They're all named monsters, so Sewer Syrup will always be whatever rank he is when he spawns.
As for how many different ranks there are... I think it's just B, A, and S? I know the lowest rank gives basically nothing and they respawn all the time. They're mainly there for achievement fodder, I think?
As for how many different ranks there are... I think it's just B, A, and S? I know the lowest rank gives basically nothing and they respawn all the time. They're mainly there for achievement fodder, I think?
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