Hello,
Placing a soulmass in the nether has caused it to keep respawning familiar ghosts nonstop. Even after I die they follow me to the overworld and begin attacking other players and other nonhostile/passive creatures such as villagers, and my farm animals. This large quantity of them has crashed the server and required me to use /kill. Please either set a default despawn time or a way to use the scythe to despawn them without using /kill

You already can de-spawn them with the scythe in hand by pressing V or any other keybind that is set to that function (check your controls). Next update will also prevent the Soulmass from spawning any ghosts if the previous ones still exist.