I've been running a game set in the Jericho Reach, and while the threat of Hive Fleet Dagon has been looming I actually have no experience with Tyranid bio-ships in Battle Fleet Gothic what did they do just rush you? I was thinking of using refluffing the Void Kraken stats given in the Koronus Beastiary. Do you think that is a good fit?

Can anyone point me in the direction of the old Battle Fleet Gothic rules for Tyranids?

Not to sure about that one. The sheer size of the void kraken vs. a ship (even a cruiser) is considerable. Try https://drive.google.com/file/d/0BxYPI8sS1DsYblpVU3NfSFVYTW8/edit

In my opinion, I believe it is a good START. In another thread, I've suggested modifying it with void shields (I like to presume that it has Zoanthrope-like warp fields, though I've never played BFG, so I don't know), warp blast-like cannons, though they might spew some sort of bio-acid that is vacuum-proof, and will eat through your hull, perhaps boarding torpedo-analogues to infect your ship with Gaunts, Lictors, Stealers, or even a Carnifex, and give it Shadow in the Warp. With the right little modifications, it could be a true terror, and with DW being more focused on the Space Marines than on ship crew who have pimped themselves into cheesedom in ship-battle, they might even be a real threat to say a Strike Cruiser, or IN vessel under Tetrarchus's forces. With it's sheer capacity to crank out more Nids, boarding it might be suicide (again, I presume it works like a big Tyrannocyte), and there may be a Norn Queen aboard, who will make Hive Tyrants look like Termagants, so yeah.

Granted, if you are playing RT in the Reach, some little bits of this are moot, as you, and your group, can be expected to have maybe pimped yourselves, in a way that only player-controlled ships usually seem to; there are a few folks on here who will post the "ideal, broken" ship design, to get so many extra achievement points, and/or field the right assortment of docks, guns, and BS/Command 120+ rolls as to render space battle unnecessary, but if you haven't done this, maybe yet, anyway, such a Hive Ship could be a severe problem for you, and the swarm dynamic isn't unique to ground forces, so there are often additional forces in its vicinity. if this works for you, best of luck, and kill some Nids, otherwise, live for the swa...BLAM!!! Sorry about that.

The Void Kraken can be a great Tyranid vessel. Also, see this PDF "Unearthed Apocrypha: The Great Devourer" by N0-1_H3R3, or a more simple but less detailed word doc "Tyranid Bioships" by Wizzardman for additional information. See this link or my link below in my signature for further information or fan related material.

Some small notes.

Tyranids use banks of explosive spores to shield themselves from weapons fire, torpedoes and strike craft. They're a shield turret analog.

Nothing says they can't use zoanthrope type shields.

Internally they use tervigons to bury intruders undet gaunts till help arrives.

The carnifex is their basic boarding unit. They need and use little else. Scale down to party sirvivability.

They open with shieldless but high armor fast escorts. Follow with light cruisers. Finish with battleship sized hive vessels.

You can take a void kracken for the escorts, but they're smaller, harder armored, travel in packs of six typically, and board with carnifexes! Halve the hp, add 3 more vu speed. No tactical sophistication. Anything bigger would need a whole lot of special rules.

Never heard of Tyranids normally boarding with Carnifexes. Figured they use Guants, Termaguants, and Genstealers mostly.

The original material from BFG suggests that tyranids use nothing but carnifexes(carnifi?) As their boarding units. It makes a horrible sort of sense. They're just bigger than medium creatures so they're rather disposable and in space combat nids have no interest in capturing ships. The example given in the books outlines the horror quite well.

Think about how you would stop this scenario, even with a skilled, powerful RT team. Somewhere along your ship a carnifex is unleashed, breaking through the outer bulkhead and depressurizing the surrounding area. It cares nothing for the niceties of atmosphere or even vaguely survivable conditions. Its target is not the crew, but rampant destruction. The fex picks a direction and heads in it. Every wall in its path is just a door that has yet to happen. Emergency bulkheads fail since they're based in sealing passages and it's making its own. Even if the bulkheads closing behind it somehow manage to contain the venting, the fex is still smashing through every plasma conduit and oxygen duct in its path so now you have plasma fires, crushed machinery, secondary explosions and enough oxygen venting to make everything an inferno. With more damage resistance than a terminator, over a hundred health, and regeneration for a cherry on top, the carnifex gives no damns until stopped with weapons that do just as much damage as the fex, it blows itself out the other side of the ship, or it's randomly crushed by another carnifex(what happened to the one in the example).

Considerably more bang for the nids buck than a mere score of gaunts.

Disturbingly, that makes perfect sense. *shrugs* It's a sci-fi game though, and killing the PC's off that easily would not be fun. I would just hand-wave that tactic belonging to a specific Hive Fleet, and not all of them conduct the same. Which, obviously, they don't. However, I still like it, and would definitely implement it at a later date.

Also don't forget the 100s M long chitin spears those things can pump out, I believe it is the BFG expansion talks about how the literately skewered a few escorts with those things. And the huge masses of disposable drone fighters used to intercept fighters/torpedoes. Yeah bio-ships should scare your crew, i think the void kraken is usable as a very small one, especially with there penitent to eat other ships.

To the original topic, using Void Kraken stats as a stand in for Tyranid bioships... no, they are not a good fit, at least not without major re-stating.

The VK from the Koronus Bestiary are only about Raider sized, and incredibly slow. They also have no ranged capabilities, only being a threat if they can get the jump on a ship in an asteroid field (where they are nearly undetectable). Tyranid ships are far more dangerous from what I know, and all but the smallest are much larger than a VK (enough to match the scale of Imperial ships)

You'd be better just custom-building a Tyranid ship than using the Void Kraken, unless you want to have a VK be part of a larger Tyranid fleet to give it some variety, then I could see it working. You could even have a Tyranid ship fling an "asteroid" at an opposing ship, only for it to suddenly sprout tentacles and grab hold when they fail to recognize it for what it is and get far enough away.