The Klingon mental and spiritual journey undertaken by a bridegroom and his closest male friends before a wedding, consisting of days of fasting, pain and other ordeals.
Kal'Hyah is the Klingon counterpart of a bachelor party, and nothing like one. Over the nights before the wedding the groom and his chosen companions pass through six trials: deprivation, blood, pain, sacrifice, anguish and death.
It is seen in You Are Cordially Invited in 2374, before the wedding of Worf and Jadzia Dax. Benjamin Sisko, Miles O'Brien, Julian Bashir, Martok and Alexander join Worf in a holosuite expecting a feast, and instead find themselves fasting in a hot cave and hanging over glowing coals.
Bashir and O'Brien spend the ordeal plotting revenge on Worf. When the wedding is nearly called off over Dax's clash with Martok's wife Sirella, they are furious to have suffered for nothing, and they get their chance to strike the couple with ma'Stakas at the ceremony's end.