Right then.
FACTION: Interloper, Drukhari
SUBFACTION: The Kabal of the Flayed Face (Commorragh outskirts)
FACTION LEADER: Archon Sraelian Juud
You know how it is. You're a minor Commorragh-born noble, not from one of the really big houses like Xelian, Kraillach or Yllithian but from one of the smaller ones that always have to struggle and don't get access to the best Webway gates. Nonetheless, your transcendant military prowess and all-around incomparable skill at anything you set your mind to makes it a simple matter to build a kabal of loyal soldiers, and your unmatched visionary genius and natural charisma further spur you to make contact with two... well, not peers, but potential allies; a Succubus who commands a respectable Wych cult and a Haemonculus who's not quite powerful enough yet that sane or non-desperate people refuse to go anywhere near it. You suggest a partnership to them - a triumvirate, allying and combining your three forces (under your banner and your ultimate strategic leadership, naturally) to gain greater rewards together than any of you could apart. Obviously you have sixteen separate plans to assassinate both of them at any given time, and you don't doubt that their inferior-but-still-potentially-dangerous intellects have come up with half a dozen each for you, but they nonetheless tentatively accept your proposal and the future is ripe for exploitation.
... well, alright, you haven't actually had any successes with your newly-forged alliance yet, save for a couple of vehicle trades and one or two joint operations against petty street gangs and beasts in Commoragh that all of you were only taking part in to scope out the others. And you may have made some, uh, rather extensive boasts and promises to your House about the successes you're going to reap by the end of the next cycle. And, yes, your two allies aren't actually committing many of their forces to serve as auxiliaries to yours until they're sure they're going to profit from it. And on top of that most of your kabalites are busy holding your position against the various other factions in Commoragh who will knife you in the back if they sense so much as a second of weakness, so you have very few to spare for away missions.
But it's all fine! Because you've gained control of a Webway Gate that opens onto a world that's always previously been more trouble than it's worth to attack, but which has now, mere months after your acquisition of the gate (clear proof of your incredible foresight), fallen into open rebellion that will leave it vulnerable to your assault! All you have to do is wreck havoc on the naval forces of the slow-witted mon-keigh who are squabbling among themselves and you'll render not only the entire system but also its neighbours easy prey for future raids, proving to one and all that you are the Archon to follow for wealth, success and power. And of course you can also improve your own position by dragging thousands of screaming mon-keigh back to your estate on the outskirts of Commoragh for sale, amusement or raw materials.
Yes. Everything will soon be coming up Sraelian, and the only things standing in your way are the pitiful, primitive mon-keigh of a half-forgotten backwater world. They'll be easy to outstrategise and defeat, and it's not like anyone else will care about this obscure little Imperium remnant.
What could go wrong?
Edit: Whoops, entirely missed the "two to four sentences" limit because I was splitting my attention between the objective types and the faction assets. My apologies. (But I had fun writing it, so I'll leave it as-is).
