These beautifully designed weapons often possessed a jeweled hilt some of which were quite valuable. They were unique as they had three perfectly equilateral edges rather than two and was incredibly sharp. The advantage they had over two edged swords was that when they were wielded skillfully, a dirhja entered a body painlessly and with little loss of blood. They were noted as being a subtle weapon when compared to an axe and used the opponent's own weaknesses against them though ultimately it always left behind a scar.
The outcome depended on the victim; if they showed courage and made no move, than depending on the wielders discretion, the blade was capable of being withdrawn. This was quite painful though the wound was curable, only leaving behind a most unusual scar. However, if the victim was craven or was a fool and struggled against the blade, then it disemboweled him with varying degrees of thoroughness.
In 2281, Liviana Charvanek used T'Shael and Cleante al-Faisal as her dirhja in an attempt to remove the Romulan Star Empires involvement in the kidnapping of the Warrantors of Peace as well as to get revenge against Spock. (TOS novel: Dwellers in the Crucible)