This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Redcap (English)
The redcap (or powrie) is a type of malevolent, murderous goblin found in Border folklore. He is said to inhabit ruined castles along the Anglo-Scottish border, especially those that were the scenes of tyranny or wicked deeds and is known for soaking his cap in the blood of his victims. He is also known as Redcomb and Bloody Cap.
Redcap is depicted as "a short, thickset old elf with long prominent teeth, skinny fingers armed with talons like eagles, large eyes of a fiery red colour, grisly hair streaming down his shoulders, iron boots, a pikestaff in his left hand, and a red cap on his head". When travellers take refuge in his lair, he flings huge stones at them and if he kills them, he soaks his cap in their blood, giving it a crimson hue.