There is 1 Reaver in MM2: the Reaver Evo knife. It was originally obtainable through the Reaver Gamepass during the 2021 Halloween Event, and later discussion online treated it as a rare/unobtainable item.

If you meant how many Reaver items/evolutions are in the Reaver set , the answer still appears to be one main Reaver item rather than multiple separate Reavers.