Ruling hope you can help.

[cynthia's fan 94]

if i knock out gengar using glisor lv.x's night slash and switch it to bench, the fainting spell doesn't work, right?

 

[Po-Po-Pocchama]

Fainting Spell does work.
If you used Uxie or Starmie LA to KO and use their effect, to put them back to your hand/deck then Gengar can NOT use it's Power.

 

[Vergere]

Yes it does. Uxie, for example, is removed from play, so it no longer exists to Knock Out. The Gliscor would still be there, even if it wasn't active.

 

[cynthia's fan 94]

ok, thank you for the help.