Of course, a Deathwatch team is no match for a Titan 'on the battlefield'. And yet, narratively, there's every reason a killteam should be able to sabotage such a thing. Even non-Deathwatch teams of Astartes are noted as being designated to such assignments (Grey Knights in "Dark Adeptus", Salamander operations along the rivers during the Third War for Armageddon, directly dispatched against Roks, Gargants and such).
But the question then remains: how would you breakdown such an assignment, in which cases should a team be thoroughly up excrement creek and when should the kill team be having the upper hand?
I've read enough of the novels and have a sufficient imagination to see alot of the room for nuance involved ("Titanicus" and "Mechanicum" illustrate such possibilities nicely), but I'm a thoroughly inexperienced GM when it comes to framing such threats as missions/objectives/trials for my players.
At the moment I'm working on a xenos titan for my own semi-supplement (a Rogue Trader oriented vehicle 'The Machination', a Demiurg titan, essentially), and I've got a good idea from Epic: Armageddon and Battlefleet Gothic to figure out its essential power level (mega, I'd say!). But looking at how to implement it as a *foe* for players, or as a tool for the players, is something I'm quite struggling with.
Does anyone have any idea how they'd go about involving such threats/targets in a game?