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Missionary ships were partially independent Kig-Yar vessels employed by the Covenant Ministry of Tranquility to explore the fringes of Covenant-controlled space. Crewed primarily by Kig-Yar, they were sent out to search and find Forerunner relics as well as new species to incorporate into the Covenant hegemony. The missionary work itself was typically conducted by Unggoy Deacons serving aboard the vessels.
The first Covenant vessel to make contact with humanity was a missionary ship, named Minor Transgression. It was destroyed during a battle with Sergeants Johnson and Byrne by its Shipmistress, Chur'R-Yar, in an attempt to kill Sgt. Johnson.
As is common with Kig-Yar vessels, missionary ships are less elegant and somewhat irregular in design in comparison to the more uniform and organic designs of most Covenant vessels. The missionary ship Minor Transgression was described as resembling a "fishhook fashioned from impractically thick wire". It had a series of segmented compartments behind its hooked prow and barbed antennae that flexed backward to a single engine in its stern. The vessel was deep blue-black in color. The ship had a single central passage leading to the bridge and a methane suite for Unggoy crewmembers. The ship was also equipped with an umbilical that the crew used to board other vessels. The ceilings of the ships' rooms, such as the bridge, had hexagonal grid patterns made of beryllium.
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