féth fíada(, féth fiada, feth fiadha, fé fíada, faeth fiadha), in Irish Mythology is a magic mist or veil which the Tuatha Dé Danann uses to enshroud themselves, rendering their presence invisible to human eyesight. féth denotes this mist in particular, and fíada originally meant "knower", then came to mean "lord, master, possessor".