## About The Pull Request
Immerse was causing harddels due to it having references to mobs. Makes
it use weakrefs for mobs instead.
## Why It's Good For The Game
Immerse would cause harddels if a mob was deleted while it was in it's
list. It could probably also happen if a turf was deleted too, but doing
that here would be much harder.
no CL since nothing playerfacing