Quick! When you hear the word mythology what cultures do you instantly think of? Greek. Norse. Egyptian. Celtic.
How about Spanish?
Ancient Spain (like ancient Italy, Germany, and most other European countries) was a collection of independent (and warring) provinces and city states. The local population shifted from Tartessian, Iberian, and Celtic to Roman, Visigoth, and others over time.
Kingdoms rose and fell, and many pocket cultures formed in Andalusia, Catalan, Galicia, the Basques, and more. And these cultures had their own legends, myths, and things that went bump in the night.
I used several of these creatures in The Broken Sword.
Beautiful female spirits who live in fresh water. They can boil the water when angry or transform into blackbirds. They can be vain and often abduct passing children, but also bring blessings to the land near their water.
Similar to the western Bigfoot, these large hairy ape-men live in the forest and were the first farmers, blacksmiths, and millers. They passed their knowledge to men, and are generally wise and helpful to humans. They also build megalithic structures.
Enormous winged serpents, these dragons are immortal but grow older and stronger over time. Like German dragons, the culebres live in caves guarding treasures. They can only be killed by swallowing a burning hot stone or food with pins concealed inside.
People who live underground crafting treasures of precious metals, which are guarded by dragons (culebres). Sound just a little like Norse dwarves, don’t they?
These little goblins appear as small, limping men in red suits and hats who like to sneak into homes at night to steal or break the owner’s possessions and cause a bit of mayhem. But if they are well-treated by the local humans, they may perform helpful chores at night instead. If you move, your trasgu will move with you, and the only way to get rid of him is to give him an impossible task. Hey, this is Dobby the House-Elf!
Beautiful fairies or nymphs who live in caves and fountains, their singing brings peace to the good and drive the wicked insane. They have a bad habit of exchanging their own babies for human ones. They also have a lot of trouble with magic, often needing help to escape from a spell.