Ok, so I'm writing up a concept for a Deathwatch campaign I've been thinking about for some time now and so I think that I'd through out the idea here and see what you think of it. My aim is, since its the first time I GM Deathwatch, to have it fairly short and focused to ensure it has a better chance of running to the end and to make sure nothing to unexpected lands on me. There are alot of things that could no doubt be cleared up but I'm hoping for some feedback from you guys. I've writen this into how I would expect the missions to be developed.
Now the game starts with the recently gathered Kill Team is sent to destroy what appears to be a Tau orbital listening post and possibly a base from where the Tau carry out special ops operations against Imperial targets. From the base information is gathered that it is in fact a research station and that artefacts from excavations of xenos ruins on the surface are gathered here. A Librarian will be able to detect that many of these items are tainted by the warp.
The next mission is of course a mission to investigate and destroy the xenos at the dig site and there the Kill Team discovers humans bearing both Tau symbols as well as what appears to be Chaos symbology, fighting on the side of the Tau. The Kill Team should hopefully get enough info to understand that the Tau are conducting research into warp technology, which the Deathwatch can't possibly allow them to aquire.
The Kill Team is now sent to board the supply vessel that normally supplies the space station and from there find out where the centre of the research is happening. After having boarded, got the information and left, the shows that an major orbital stations is the centre but it is far to heavily defended for an attack right now.
Instead its decided that the Kill Team will hinder the Xenos investigation, but to reach another three sites its decided that the Imperial Guard will launch a major offensive to give the Deathwatch some noise to operate behind. The Kill Team is sent to destroy a Tau communications and coordination central which is connected with Tau surface-to-air and surface-to-orbit batteries that makes Imperial use of air power or orbital bombardment both hazardous as well as forcing to to operate with limited efficiency. At the station the Kill Team finds both Tau and more Chaos tainted advisors to the local Tau commander, in this case a rogue Imperial pilot, who gleefully see the aliens destroy Imperial aircrafts with his knowledge of how the Imperials work with their air forces.
After neutralizing the central a Thunderhawk transports the Kill Team to the first Xenos site and there they encounter pretty much the same thing as the first site. At this point however some of the aliens wake up and it becomes a three way battle before the Kill Team detonates a charge to destroy the ruins. But after this is done they are informed that contact with the Kill Team sent to the largest of the ruins has been lost, they are to investigate. At the site the Kill Team finds a jaming device, the dead Kill Team and the last enemy forces that have yet to evacuatethe area, including three Chaos Space Marines. New orders are to engage the enemy and ensure that none of the Traitor Marines are allowed to escape.
After this revelation it becomes apparent that the Tau plans with the Archenemy must be stopped. In order to assault the orbital station the Watch Commander and the Ordo Xenos decides to support a plan proposed some time ago to help turn the tide of war. The idea is to use a specifically mind-wiped, programmed and mentally conditioned staff officer to fake a defection to the Tau, give some information to the Tau and when possible to assassinate the planets Etheral. This should demoralize the fire warriors enough so that an attack can be launched on the orbital station. To give credience to the infiltrator the Kill Team will make a faked assassination attempt on the defector. Once there the Kill Team discovers that there are several threats to the agent, including a mind-reading psyker and a Water Caste expert on humans, both of whom could reveal the infiltrator for what he is and thus they must be killed to ensure the success of the mission.
After that the Tau have taken the infiltrator to them he gives them information that allows them to reverse several Imperial gains and in a month of heavy fighting kill or capture close to a million guardsmen with their equipment; several thousand pieces of artillery, many hundred aircrafts and at least seven thousand vehicles of different types as well as destoy a number of supply depots. But this is a price that must be paid because this makes the Tau move the infiltrator the orbital station. And here he gets a chance to kill the Etheral and send a psychic signal to the Inquisitor's personal Astropath. When this signal comes a strike force immedietly sets out to attack the station with at least a dozen capital ships with escorts that smashed the demoralized Tau defenders aside and launches several thousands of troops to board the station and divert the enemy from the three Kill Teams sent to take down major systems and locate and destroy everything connected to the warp-research. The battle becomes bloody when the Tau reacts with a fury to the Imperial invaders. Half way into the station the warp engine is started and the station is flooded in warp energy and it becomes a four sided battle royal: the Imperials, Tau and allies, Chaos warband that turns on their erstwhile allies and ramapging daemons that fight anyone they come across including daemons serving other masters or even the same masters. I'm thinking of a real nightmare scenario that the Kill Team must push through to finally reach the warp engine where the Chaos Champion faces them, after they have dispatched his personal guard.