Not sure whether this was supposed to be in gameplay or story, but point is, Kalista's W doesn't make much thematic sense.
Her W's PASSIVE does, but the active essentially creates a moving ward. How does that tie into her theme of a spirit of vengeance? It would make sense if it was on some sort of sentinel or scout-themed champion like Teemo or Galio but why Kalista? A moving ward doesn't really scream 'VENGEANCE', more like 'I will protect you!'
Kalista isn't a person. She's a vast collection of souls that have sworn themselves to vengeance. Her 'soulbound' is one of the souls that she has marked and will absorb into the collective soon enough. I imagine the scouts are simply spirits that she tears from herself and assigns a purpose (in this case, scouting).
She sends a soul that she collected to scout.
If there is anything in her kit that makes no thematic sense, it's her passive
Her ult doesn't make sense either
According to her lore they summon HER when she is soul bound to someone
meaning that when she ults she should jump to THEM not the other way around
