The final Star Power mission, and the boss fight against Gaunt. A shieldbreaker is pretty essential here, and an armor breaker sure can't hurt.
When ready, hit the marker down by the shield wall
Your first task is a lair. It is, at least, close by, and should have a number of loot boxes. Hack and enter as per usual.
The first challenge room will be your formal introduction to the bufftrooper.
You've probably encountered them before now, and as ever you want to be sure to shoot at them, and not whomever they're empowering. The bufftrooper's buff isn't just super toughness or superfast healing, it's invincibility- so don't waste your ammo on his beneficiaries until they've stopped glowing.
Clearing out the first wave summons a huge second wave. Unusually for this layout, you do have stick around until they're all dead. Not unusually at all, you can still use the upper balconies for cover and disrupt enemy movements if you're getting sandbagged.
The next room is another required killfest, and again the enemy are headed by bufftroopers.
It's a big room, so don't let yourself get pinned down. When done, remember to scan for boxes here and in the hall to the next elevator down.
Another big round room with an exterminate-all-LEGION objective. The main threat here is the central posse of snipers, backed by a bufftrooper commander. Keep an eye on your surroundings- some of the 'windows' between you and the snipers are just empty space.
This the last big fight (of the lair, at least), and you'll have to knock down a lot of basic cannonfodder. When the carnage finally ends, pick up the keycard as directed.
In the next room it only takes a simple hack to destroy Gaunt's production line, then it's a mad sprint to the exit as the place explodes around you. Remember to use your dashes, and switch out characters if you start taking too much of a beating.
You might also keep an eye out for loot crates as you go, but they're hardly essential. When you reach the elevator, return surfaceward and get in your car, which will now be the Hammerhead, regardless of previous choices. Drive to the concert- you've got four mintues on the clock to start, and driving through markers does *not* grant a time bonus this time out.
Still, the time limit isn't very severe. Once your route reaches the riverbed however, keep a finger close to the Boost key, and hit it once you see the final ramp- you'll need to to clear the special jump Mixer has prepared for you.
Landing the jump puts you at the venue- follow your marker in and confront Gaunt. He's shielded and armored, and his thrown cluster of purple grenades do real damage. It's a balancing act to keep taking down his shield while maneuvering around enough to avoid blasts, but Fortune's a natural, and Oni can use his cloak to find a little respite while lining up his next shot.
Taking out his armor triggers battle phase two. Now you're facing elite helltroopers (roadies) and bufftroopers (stagehands). Keep moving, using the terrain to separate individuals from the herd,where they can be taken down without distraction. If you end up getting ambushed yourself, note the health dispensers under the stairs.
The final wave will be headed by an elite stage manager (nee snipetrooper). Finish them off (not a bad use for your accumulated MAYHEM) to trigger the next phase.
Here you'll be mobbed by Gaunt fans- use melee attacks to free them from mindcontrol (not all character's melee attacks have the same shape- you'll want to pick something like Fortune's roundhouse kick or Hardtack's spear to clock as many enemies at once as you can).
Every time you dispatch a wave of Gauntites, you then have a few moments to hack one of the indicated terminals. These cannot be bypassed by a master programmer, and must be hacked normally. The first will have two hotspots, the second three hotspots, and the last one will be the first four-hotspot terminal in the game.
Hack that and it's the end of the mission, and the end of Gaunt.