2020-11-10 : As Fleshbag Marauder's ability resolves, first the player whose turn it is chooses a creature to sacrifice, then each other player in turn order does the same knowing the choices made before them. Then all those creatures are sacrificed simultaneously.

2020-11-10 : When its ability resolves, you may sacrifice Fleshbag Marauder itself. If you control no other creatures, you'll have to sacrifice Fleshbag Marauder.