I have just a few questions with this card.

It doesn't exhaust so when does this cards effect's end? Is it just a typo and ffg accidentally left exhaust off the card.

Does it only effect people when the card is cast or if a monster or investigator moves in after it's cast then do they suffer the effects?

And it effects the area the caster is in correct? so the caster would take a stamina loss when the card is cast?

Thanks for any help you're able to give me.

1. All spells exhaust when cast: this is a typo. Of course, some spells are discarded if you succeed (Bind Monster).
2. Its effects are. I believe, for that investigator's movement phase. If the investigator battles multiple monsters that movement phase, they will all have the toughness reduction. I am not sure whether it works for the ENTIRE movement phase—i.e. another investigator can then move in and the monsters will have reduced toughness. In either case, it's for this turn only so the monsters DO revert back. This of course means that other monsters moving in later will be unaffected, as the spell will have worn off.
3. The caster loses stamina. If the caster reaches 0 sanity and stamina this way, he will be devoured!