According to legend the Pooka was a night-dwelling spirit that took many forms but was almost always destructive, malicious, and inimical in manner, although in some stories it was seen as more mischievious than evil - the Pooka was fairly unique amongst the fay (or fairies) in the fact it took a different form depending on the region of Ireland it occupied and due to its shape-shifting and trickery it was one of Ireland's most feared creatures.
The Pooka often took the form of a black horse with yellow eyes and wild mane and would roam large areas of countryside at night, tearing down fences and gates, scattering livestock in terror, trampling crops and generally doing damage around remote farms.
In remote areas of County Down , the Pook took the form of a small, deformed goblin who demanded a share of the crop at the end of the harvest: for this reason several strands, known as the 'pooka's share', were left behind by the reapers. In parts of County Laois , the pooka became a huge, hairy bogeyman who terrified those abroad at night; in Waterford and Wexford, it appeared as an eagle with a massive wingspan; and in Roscommon, as a black goat with curling horns.
The mere sight of it prevented hens laying their eggs or cows giving milk, and it was the curse of all late night travellers as it is known to swoop them up on to its back and then throw them into muddy ditches or bogholes. The pooka had the power of human speech, and it was known to stop in front of certain houses and call out the names of those it wanted to take upon its midnight dashes. If that person refused the pooka would vandalise their property because it was a very vindictive fairy.
- The púca has counterparts throughout the Celtic cultures of Northwest Europe. For instance in Welsh mythology it is named the Pwca or Pwwka and in Cornish the Bucca. In the Channel Islands, the Pouque were said to fairies who lived near ancient stones; in Guernésiais and Jèrriais, a Cromlech is referred to as a pouquelée or pouquelay(e), poulpiquet/polpegan are corresponding terms in Britany.
- The origin of the name may have come from the Old Norse term pook or puki, which refers to a "nature spirit". In Germanic languages, such as Frisian or English, this became pucel, pook or puck.