Welp. Here goes nothing. Sorry for being rusty.
The Next Front
(This is the first mission of FoG, and it has a certain Cutscene to it, much like how TTK started. The location is Dusty Memorial, Deimos; It shows an old building, hinted to be a research station, taken over by the new Fallen House of Scar. Fallen Dregs are seen patrolling around the perimeter of the roof, decked in Orange coloring. Their leader, Beriks, is revealed to be behind them shortly after. The patrol stops abruptly, and in the distance, sounds akin to lightning can be heard. Fallen all around the base look up at the sky, seeing a bright laser moving towards them. Those on the roof quickly jump off, the building being destroyed in a blaze just after they get off. In the sky, several more are falling, some hitting Fallen, some causing landslides of dust, and yet more tearing up the ground below. The station, now completely on fire, is shown collapsing into a gaping hole. Camera cuts to Beriks running into a Skiff, taking off shortly after. Shots of Burning Legion slaughtering and capturing Vandals and Dregs, the damage caused by the blasts, etc. It ends on an overhead view of where the base was, now just several craters and a burning building.)
(Cuts to the Guardian, flying past Mars. Cayde begins speaking over the comms.)
Cayde: Okay, Guardian, we back the tower are being bombarded with all kinds of info on the Cabal attack on Deimos. Superweapon has been launched, they say, City is doomed, Warlocks yell...But there has to be a reason why the surface of the planet looks like Swiss cheese.
(The Guardian's ship has broken past orbit, into Deimos. The moon is shown to have a cracked, crater appearance, similar to the Moon. Golden Age remnants lay in midst of the craters.)
Zavala: All the senseless destruction... The allies of the Darkness have but one purpose, to destroy everything that stands. We need to assess the threat of this new legion and weapon, Guardian; Or we soon end up as the Fallen that are before you.
(The Guardian lands on the surface, in a very deep hole filled with Fallen remains and corpses. This is where the player spawns; The Remnants, Deimos. I'm imagining a large hole with different platforms and such leading up to the surface. There would be makeshift platforms which Fallen have made, and corpses to hint about the Cabal's arrival. The Guardian heads up top, only to find a futuristic Cabal site up, in red and yellow coloring.)
Ghost: Cabal installations...They set these up overnight, but why? This planet has nothing valuable to extract, and all the Fallen are gone. We need to get inside and figure out. I'm detecting some movement near here, maybe it's a scout party we can take a key from.
(Sure enough, a hill leading to the Inferno Memorial had a great view of the new Burning Legion enemies. The Guardian has a small firefight with them, but overpowers them and takes the key.)
Ghost: Perfect. Now, let's get inside. I'm really starting to wonder what they're doing here...
(The Guardian sprints to the Cabal site, using the key to get inside. Inside, trails of liquid and oil lead into a room, where Vandals, Dregs, and Captains are all seen behind glass being executed one by one.)
Ghost: Strange...It's not in Cabal nature to take prisoners like this. This Legion must work things differently than others.
(Added several rooms of fighting Burning Legion Cabal, the Guardian encounters a large loading bay full of Harvester and other futuristic Cabal tech. One of the Harvesters, however, takes off and starts firing down below.)
Ghost: That ship is going rogue! We'd better slip-...Wait. I'm detecting...Light? That can't be right...That would mean...
Cayde: Hey, so, how's the expedit-Woah. Some Cabal soldier must've gotten mad at someone stealing a kill, eh?
Ghost: No. There's a Guardian in there...
Cayde: What? Impossible, there's no Guardian that can-...(Quietly) Well, I'll be damned.
Ghost: Who is it?
Cayde: Long story-...look. I need you to trust me on this one. Help that Harvester out. He's a Guardian alright, and it looks like he finally decided to come out of hiding...
(The Guardian helps the Harvester take out ground troops and a modified, enormous Goliath tank, a Scorch Roller, for a final boss. Afterwards, a small Cutscene appears, showing the Harvester hovering in the air. In a dramatic reveal, a figure jumps down from it, dressed in Hunter-like armor, pelts, and with several different pieces of weaponry.)
????: I appreciate the help, Guardian. Of course, your prescene is a gift in itself...
Ghost: Wait, come again?
????: Don't be humble, Ghost. I've heard of your countless escapades back home. The Black Heart, Crota, Skolas, The Taken King...You really have come a long way from when they found you.
Guardian: Then...Who are you?
????: Real name isn't used much, probably only by the Vanguard. They call me the Frontier Master...You can know me as Cyrus.
Ghost: How do we know-Wow. I got his file, and there is a LONG list of achievements here...
Cyrus: Most of it was Cabal assassinations, thus is why I'm here. But now I have another task. Guardian...There's a reason I left the Vanguard. I figured it wasn't doing enough. Sure, take out the enemies. Then what? They just come back. I saw a different way of doing things.
Ghost: I'm not following you...
Cyrus: Let me finish. See, since they have their own unique weaponry, vehicles...I figured. "What can't we use that for themselves?". There's strength in unity, Guardian. And if we followed the old saying "Enemy of my enemy is my ally", then I'd bet we'd get problems solved faster.
(He looks at the Fallen Scar members, executed against what was a firing squad, now scorched remains.)
Cyrus: Look, allying with the Darkness is a sin in its own right, but if we can throw it back at itself...Then maybe we'd have more leverage. More leverage, more power. More power, more wins for the Traveller. Head back to the Vangaurd, tell them what I told you. I'd do myself, but I have a job to do.
(He jumps into a Skiff-like Jumpship, leaving the hangar. The Guardian and the Ghost look at each other for a brief second before their Jumpship arrives and carries them off. Imagine this scene with some dramatic music.)
This was all I could get for now...