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.
THE GNOMES OF UDNALOR: Part I
Upon entering the deep underrealm of Udnalor, one must first pass through the upper halls, which were the residences of the gnomes in days of past glories. Now they have abandoned the fading tapestries to the worms and moles, and an uncanny silence reigns, laid over the oaken tables like the thick layers of dust and humus.
There may be creatures which now inhabit these areas: nests livid with giant maggots, rats and other vermin.
The watchtowers and passageways which lead to the Overground are frequently trodden, however. After all it takes a great many small humanoids to hoist a single giant rabbit corpse back through the fathoms of earth.
The gnomes primarily hunt giant rabbits with bows and arrows tipped with the subterranean poisons concocted by their best alchemists.