Chaos Escort
The smallest and most common type of warship available, Chaos Escorts are lightly armed and armored, but compensate for this by being extremely fast and maneuverable. As their designation suggests, they often accompany larger ships during fleet actions, screening them against torpedo attacks or enemy escorts.
In the Fleets of Chaos, Escorts normally act as raiders, penetrating deep into Imperial Space to prey on vulnerable supply ships and transports. Weak individually, such Raiders group up in squadrons for both mutual protection.
Escorts fall under two broad types: the much larger Raider, which is better-armed and protected, and the smaller Destroyer, which is a lot nimbler and faster.
Escort Classes
Raider
Idolator
Said to be the product of the Dark Mechanicus Forge World of Xana II, the Idolator-class Raider incorporate features and systems of possibly xenos origin. These ships also infamous for their incredible long-ranged gunnery, which point to a targeting system that Adeptus Mechanicus cannot readily duplicate.
The Idolator is armed with a short-ranged front-facing Lance battery as well as a mid-ranged Weapons Battery.
Infidel
Meant to replace the Cobra-class Destroyer, the designs were found to have been stolen. A few years later, ships bearing the same description were reported to be attacking Imperial supply convoys. As a result of this, the class was redesignated as the Infidel.
The Infidel is armed with front Torpedo tubes, as well as a short-ranged Weapons Battery in front.
Destroyer
Iconoclast
A constant peril to shipping, roving squadrons of these Destroyers are a regular part of pirate fleets. Weak on their own, this is normally compensated by sheer numbers, and enough Destroyers working together can even bring down a Cruiser.
The Iconoclast itself is armed by a short-ranged Weapons Battery turret. Sooo...what are those tubes on the sides for if not guns or torpedoes? Chaos, that’s what. Being crazy-stupid for its own sake.
...This ship does look pretty cool, though. Rogue Traders like it.
In Battlefleet Gothic
The cheapest and smallest ship type available, the Escorts are also some of the fastest and agile ships available. There is no limit to the number of Escorts that can be included in a list except points, so use them to round of a fleet.
That aside, use Escorts to screen your much more expensive units from Ordinance or Torpedoes, or harass isolated ships.
In Battlefleet Gothic: Armada 1 & 2
Much like their counterparts on the tabletop, Escorts are cheap and quick ships. Aside from their obvious role as Torpedo screens for much more expensive vessels, they've also been used as scouts and spotters.