ISV Merciless

One of the five vessels in the convoy sent by the Empire from Gododdin to Nemavand and captured/destroyed en route. Discovered by the Imperial Red Company during the famed "Battle of the Beast." Attached to the 337th Sagittarine Legion.

The Other Four Starships:

ISV Valiant

ISV Old Iron King

ISV Emperor's Hand

ISV Red Defender

The Merciless held just over nine thousand men, for it was far smaller than the Tamerlane. They’d been packed on ice like salt fish, never intended to be pulled from their berths for deployment in transit, never intended to awaken until they reached Nemavand.
...
The Merciless had two five-terawatt lasers, each one powerful enough to level a city block. The weapons were of little use against shielded targets, but against unshielded foes? They could destroy a target faster than they could react, making them the ideal first assault weapon of choice in any ship-to-ship ambush.

Demon in White, Chapter 24: Beyond the Doors of the Dark

Udax and his men had broken up into groups of five or so, each standing guard at one of the six airlocks—three to a side—that ran along the length of the Merciless.
...
Like most Imperial starships, the Merciless had dozens of turrets and gun emplacements on its outer hull designed to repel boarding craft. A last line of defense should the aquilarii fail.

Demon in White, Chapter 25: In the Belly of the Whale