Quick brief on the situation:

• Previously ran a Dark Heresy campaign centred on a splinter faction of the logicians. They had been subverted by a genestealer cult (hence the 'splinter faction' and were doing naughty things with a stolen exterminatus warhead). The characters (more or less) survived and were 'boxed up' for future use.
• Currently running a Rogue Trader campaign with a heavy Yu'Vath theme. The Rogue Trader himself has a ship with salvaged Shard Batteries, has already played through the Forsaken Bounty adventure, and I have a few other ideas for assorted Yu'Vath holdovers.
• The next campaign after this one is likely to be the Haarlock Legacy. It's likely that some players will want to join from the previous =][= campaign (easy enough), but also that some of the Rogue Trader characters - especially the ship's arch-militant - will want to join, bringing along their characters.
• I could do with suggestions for how to get them involved. Acting as transport for an inquisitor (Sholto Unwerth fashion) is traditional, but not really that useful in this case. Let's say that the Rogue Trader left the Calixis sector in a hurry, and didn't stop to pack. An Inquisitor turning up on Port Wander has about a one-in-three chance of being there looking for him .
• The best way I can think of, is to actually have the first Haarlock Legacy mission be a Rogue Trader endeavour. I'm not sure if it's realistic for Erasmus Haarlock to have got as far as the Koronus Expanse (since the Calyx expanse wasn't yet the Calixis sector at this point). Having some leftover messing-around-with-time/warp/reality device makes sense, and that seems to be a Yu'Vath* speciality.

Any thoughts/suggestions/adventure seeds graciously welcomed.

* P.S. in case it matters to your suggestions - the Yu'Vath do not, and did not, so far as I'm concerned, actually exist as such. The xenoforms which emerge from a halo device (which the Yu'Vath are known to have made) bonded to a human (or anything else) are/were the Yu'Vath. So the 'alien race' with its human slaves, was actually all humans (originally), not that anyone knows that. However, it means that a sufficient density of halo devices (and Yu'Vath tech seems to be self-replicating and sentient of its own accord - see the Psycharus Worm and the Whisperer) and enough time can effectively bring the 'species' back from extinction.