I did some thinking, here are some ideas for a Grey knights barge
May -only- be taken in a pure Grey knights fleet. Only an Ordo-Malleus Inquisitor lord is allowed to be embarked on this vessel.
Grey Knights Battle Barge "Penitent Warrior" 440 points
Battleship/12 20cm, 45o, 6+ armor, 4 shields, 4 turrets
Armament
Port st 12 weapon batteries 45cm L
starboard st 12 weapon batteries 45cm R
Dorsal Bombardment cannon st 8 FLR 30cm
Prow Torpedo's St 6 F
Prow Thunderhawk Bay st 3.
Special Rules:
May not CTNH.
Chariot of Purity: The Penitent Warrior displays the very height of Imperial technology, with power and engine systems that are the envy of other chapters. This vessel rolls an additional 1d6 on all ahead full special orders. The Penitent warrior is covered in protective runes and sigils that negate the effects of the marks of chaos.
The Penitent Warrior may replace it's prow torpedo's with the following weapon systems for no extra cost
Prow bombardment cannon, st 8 30cm F
Prow Psychic Cannon, st 1 45cm F
Prow Lance, st 3 30cm FLR
You may take the Penitent Warrior in a fleet of at least 1500 points, must embark an Ordos Malleus inquisitor lord, and only take Grey Knights Strike Cruisers and space marine strike craft to support it.
The Psychic Cannon: An ancient device of mysterious origin, it fires a massive blast of psychic energy at a target vessel. Designed to destroy or banish demon ships, it is still capable of incapacitating other vessels, and follows the following rules.
The psychic cannon fires like a lance, but hits on a 5+ (as it is more difficult to aim). It may not be fired if the ship is crippled.
If it strikes a ship with shields up, place a blast marker on the vessel as if it were hit with a normal lance.
If it strikes a ship with it's shields down, it causes one point of damage, and the following effect takes place:
IF a Demonship: It is immediately thrown back to the warp, and on a 4+, is destroyed. If not destroyed it cannot heal the damage dealt by the psychic cannon.
IF a normal ship: The vessel's weapon strength is halved for the next round
If a Tyranid ship: Synaptic control is knocked out for that vessel for one round. (if this is a hive ship, you cannot use it for re-rolls or rolling leadership. It's weapons are not effected).
The above effects DO NOT HAPPEN if the attack was successfully braced.