The spirit of a creature trapped in amber cannot escape to it’s afterlife / next incarnation / whatever.
Such trapped spirits can be contacted by those who know the right rituals and magical power derived from them – typically the power to control one individual of that species.
Can by quite powerful if the creature is a colony insect (ant, bee, wasp, etc) – simply control the queen and you command the whole colony.
A large river that is continuously covered in a thick layer of fog. There will be either a rope ferry to get across or possibly a boat that is rowed across by worshippers of the water elementals. It is very thick fog to the point where it even muffles voices even at close range and visibility even beyond a foot is almost impossible.