Ushaan

From Memory Alpha, the free Star Trek reference.

The Ushaan is a crucial part of Andorian tradition, a code of honor demanding a duel to the death in which the combatants fight against each other with an ice miner's tool, the ushaan-tor. An enormous body of rules and regulations exists around this code of honor, summing up to 12,000 amendments.

The Ushaan can be demanded by someone as a means of personal vengeance, for example to avenge a personal loss. However, there exists a right of substitution, allowing each combatant to put up a replacement for themselves. Furthermore a married combatant can postpone a duel indefinitely, if there are no children to continue their clan. Additionally, the fight may be called off, if one combatant disables the other in such a way that they cannot continue the duel.

Commander Shran challenged the Tellarite Naarg to Ushaan in 2154 after Naarg caused the death of Shran's lover Talas. To prevent a diplomatic incident, Jonathan Archer fought in Naarg's place. The Ushaan was settled when Archer incapacitated Shran by severing his left antenna. (ENT: "United")

The Ushaan ritual was first mentioned in The Andorians: Among the Clans, a Last Unicorn Games sourcebook published in 1999.