"Geas" and "Geasa" redirect here. For the heavy metal band, see Geasa In Irish mythology and folklore, a geis (//, plural geasa) is an idiosyncratic taboo, whether of obligation or prohibition, similar to being under a vow or spell.Geasa in Irish MythologyA geis can be compared with a curse or, paradoxically, a gift. If someone under a geis violates the associated taboo, the infractor will suffer dishonour or even death. On the other hand, the observing of one's geasa is believed to b