At inbetween times and inbetween places, the barriers between the worlds weaken, and folk can more easily pass from one realm to another -- or so they say it used to be.
In the Tapestry of Cumbria,
Gwen knows of the powerful Fair Folk (whom the norse called Æsir),
the shapeshifting Wild Ones (Vanir, to the norse) and the wee bogans.
She knows of hideous hags and ogres (trolls or dark elves to the norse),
giants who once roamed the world of mankind,
and knockers, metal-workers who delve deep underground.
Common mythological threads run through various cultures in Europe. Celtic lore and Roman mythology share concepts with the Teutonic. Norse sagas spell out most clearly the kinds of beings that might stray into our realm from one of the Otherworlds.
How many Other Worlds are there, you may ask?
Norse sagas tell of nine worlds ranged about the great ash tree Yggdrasil . Odin's eagle perches in the uppermost branches, looking down on all, and gives messages to the squirrel that races up and down the massive trunk.
Closest to the top is Odin's realm, Asgard where dwell the Æsir. Not far below is Vanaheim, home of the Vanir, and Alfheim, home of the Alfar.
Perhaps one of the high peaks of Asgard was known to the ancient Romans as Olympus.
The squirrel scurries downward out of the glorious upper branches. It passes the world of mankind (Midtgard, or "Middle Earth"), Utgard ("Outer Earth" where be giants), Svartalfheim (home of the dark elves we might call trolls), and Nidavellir (the Nether Plains, realm of the dwarves).
Tales blur the distinctions between these worlds and their inhabitants. Some trolls grow large as giants, and are by nature both clever and evil. Many giants are gentle, some stupid, others have a taste for manflesh. Some tales equate trolls to dwarves, for both prefer to live below ground; but trolls live off plunder and slave labor while dwarves delve for ore and gems and master the smithing of precious metals.
The squirrel scrabbles further down the trunk of Yggdrasil to the last two worlds:
Muspell, land of fire and flame (and dragons?),
and Niflheim: land of ice, ruled by frost giants.
At the roots of the great tree, the Norns watch over the well of Urda, but the squirrel passes them by. It seeks not the Norns but the great serpent that gnaws at the tree. The squirrel delivers the eagle's message of taunts and jeers. The monstrous beast roars its reply laden with insult, and the squirrel dashes up the ash again, a chattering gossip-monger employed in the unending feud.
We the folk of Midtgard have many and varied tales of Otherworldly beings come a-roaming through our world, wielding powers beyond our imagining. Zeus could cast lightning bolts. So could Thor. They rode out of the sky in chariots pulled by fantastic creatures, or rose from the depths of the sea. Wee folk popped out of holes in the ground, or from hollow oaks, and worked mischief on ill-mannered humans.
If you were truly lucky -- or unlucky, as the case may be -- you might wander into a far realm yourself, if you crossed a threshold at an inbetween time. Any boundary between land and water, or water and air, or land and air (like the brow of a hill), could form a threshold between our world and a mystical one. Treacherous to mankind is any place that is neither here nor there but something "other" inbetween, like the doorstep between indoors and out of doors, or a cave entrance between above-ground and below-ground.
The Romans knew of this concept. Their word for threshold, "limen," leads to the term "liminality" which describes the stepping from one world into another.
Many cultures warn of the danger of lingering too long in other realms. Take care, if whisked over yon, never to eat a bite or drink a drop of any faerie fare. If you do partake, you'll find your own world changed when you return. Days or months or even years will have sped past, so beware! 'Tis wisest to refuse whatever morsels are offered.
You do want to come home again, don't you?