Nemesis-class Sloop

While it is technically classed as a system patrol and defence vessel, the Nemesis-class Sloop is a highly aggressive vessel, designed with combating incursions by stealth vessels. Armed with advanced sensors and weaponry, the Nemesis-class can quietly and passively monitor for enemy ships, then accurately take them down from range. Fast, and armed with stealth technologies of its own, it usually operates in a planetary, or system defence role, or an escort role. It has also been seen as a support vessel for fleets, protecting their flanks, and moving ahead to check for enemy reconnaissance vessels. 
These vessels have been an enormous boon to the UNSC, with the UNSC Black Swan accounting for 14 vessels, and 19 more assisted.
==Ships of the line==
*UNSC Nemesis
*UNSC Black Swan