What or whom could threaten a magical kingdom in fiction? E.g. an power in the east that wants power

NOTE: These are different scenarios, not continuations.

The antagonist (villain) seeks the secret magic artifact in the kingdom that would increase his power.

The antagonist wishes to enslave the world. He gathers an army and attempts to raid the kingdom.

The antagonist has a grudge on the emperor of the kingdom, and tries to storm the kingdom to kill the emperor. OR, the antagonist blames the emperor for, say, a death of a relative/someone close to them, and tries to kill them for said reason.

Classic aliens that come down and try to take over/destroy the planet (including the kingdom).

Ogres/trolls/dragons etc start to attack the village.

An unknown evil in the north/east/south/west is powering up a powerful attack that will destroy the kingdoms magical force fields (if they have any) and completely obliterate the kingdom in one shot. A group of amateur or professional mages travel across the land to stop this from happening (sort of like Lord of The Rings).

Just some ideas.