At the beginning of an adventure, the party will be hired or stumble upon an opportunity, often sit down to make a plan. Going over the information they collected, sitting around a corner table in a dimly-lit tavern and putting their heads together, discussing whether to accept the mission, various possible approaches and arguing over the level of violence they wish to employ.
In Fallen Empire, you, the players, do not have to spend this time if you do not want to. There are several game mechanics to support the notion that the characters have decided to go on this adventure, made a plan, and prepared for the adventure, without playing out all this pre-adventure work.
First, establish the motivation of the party. Why are they here and why are they going on this adventure? What do they hope to gain? What do they stand to lose?
At this point, the characters may have incomplete information and things may later turn out not to be as they seem. But for the moment, with what they know, we establish why they are on this adventure at all.
This is not a roll or a challenge, but a discussion between the GM and the players, including the players with each other. Since you, the players, have already decided to play this session together, the question is not if, but how and why. Do your characters know each other or is it a chance meeting? Do they expect a reward or do they work against a threat? Why do they fight and not just run away?
You can set up conflict between the characters here, if you want. However, keep in mind that you, the players, are playing this session together, so you should not give your characters motivations that would stand in the way of working with each other, at least reluctantly. Don't build in time bombs that make the party split up at the first sign of trouble.
Establish at least answers to these three question - noting that different characters may have different answers:
After establishing the why, move to the how. Instead of a detailed plan, the players merely decide upon a rough outline of a plan. Do they want to bash down the front door, swords in hand? Or sneak in through the back alley? Or bluff their way in with their superior social skills?
In fact, the GM can start off the entire adventure with the first interesting scene, setting it up with a short prolog about how the party was hired or stumbled into the adventure, and only asking for this rough approach, and then proceed to the Engagement Roll.
Using flashbacks, any other things the party has prepared beforehand can be established during the adventure.
You can, of course, actually play out the meeting, quest accepting, planning and preparation phases if you prefer and everyone enjoys doing so. The game offers you the possibility of skipping straight to the action, but does not force you to do so. If you decide to play things out, you do not make an engagement roll.
Once the party has established their initial approach to the adventure, a fortune roll establishes how well this works.
Normally, as a fortune roll, this would be just 1 die for sheer luck, but given the circumstances, the engagement roll could also be made with:
The outcome of the engagement roll determines how the adventure starts off:
The party decides to storm straight into a goblin hideout. Several characters are good melee fighters, and the goblins are weak creatures, so the GM decides that they are at an advantage for their engagement roll.
The 2d6 come up 2 and 5 for a result of 5 - a partial success.
The action starts with the characters having broken through the entrance, but the goblins had time to grab their weapons and are ready to fight. The initial position of the characters for the fight is risky.
Planning and engagement are slightly simplified compared to Blades.