Sylphids (sylphs as masculine) are air elemental spirits who may come from celtic, gallo-roman and germanic mythologies. They are especially known through the work of Paracelse.
They are positive beings who give inspiration to artists and symbolize beauty, subtility and spirituality.
Valkyries are minor "dís" divinities from Nordic mythology, similar to Norns. They are armored women riding wolves who lead armies on the battlefield, deliver death and bring fallen heroes to Valhalla. Connected to Odin as servants and preparing for battle for Ragnarök, they are also sometimes lover with mortal beings and can be associated with shield-maiden, the female warriors from Scandinavian folklore.