You're creating depth an positioning in what is essentially two channels and the interpretation of position comes from the difference in volume from L to R (assuming you're not doing 5.1 this is audacity). More whispers at different volumes and positions the more of a chorus you will get. I can't tell you how many to add but you know add some. If you record low bitrate time shifting to accomplish a pitch shift will sound like shit. Do your best to do it in the pitch you want and for the length you want.

There is some echo/delay and reverb added for 'space' maybe some doppler going on There is a lot of panning happening from the L/R channel to give it a swirling position in the soundstage The whispers sounds like the same one saying 'touch the and it doesn't change it's just played multiple times so you can use one whisper clip Environmental cues are happening to give presence and set the stage and extra voices that kinda sound like muffled talking starting around like 00:00:12

Foley accents for the cave and the walking

Whispering sound effects free