I’ve made some tests on the map “Contingency contract : Deserted Factory”.
I don’t know if these are bugs. Someone should report if they are.
First, Sora’s S1 inflict sleep and cut all sounds in the game.
Blemshine’s S2 don’t have this effect.
Second, Mephisto is immune to sleep(Sora and Blemshine) and all operators can hit him during a sleep skill.
Maybe all boss in the game are immune to sleep? this will reduce the sleep utility.