Chapter 7 takes you to the Steyliff Grove dungeon and two tough boss battles. Get Chapter 6 mopped up then take the ride to the Vesterpool area to get started.
Party of Three, Steyliff Grove
As you drive you'll encounter a roadblock with a handful of Imperial troops and an MA Veles mech. After defeating it pay close attention to the map: the road forks just before you get to the long bridge, and it's important you take the dirt road rather than the bridge.
The road you want is marked in yellow on the Regalia's navigation map; attempting to cross the bridge will lead to an almost certainly unwinnable fight.
Make your way down the hill towards the Vesperpool, park the car on the loop of road near the marker, and walk down the path to meet up with Ardyn. Follow him through the undergrowth and then speak to Aranea. You can't enter the dungeon until nightfall so kill some time by exploring the area for items, doing a spot of fishing, and restocking, and head for the marker once the sun has set (5pm should do it).
Make your way down the long stairs and take the exit to the left in the first room. In the second room you'll be ambushed by some Skeletons (vulnerable to Broadswords, Machinery and Frost), and turn left into the corridor once they're dealt with.
Turn right at the end to emerge onto a balcony inside a large open room and head towards the marker - on the platform sticking out you'll be attacked by some Crème Brûlées, slightly tougher versions of the Flans you met previously, along with a few more Skeletons.
Descend the stairs at the end and move along to the end and down another set of stairs, dealing with the Crème Brûlées on the balcony again. Head towards the marker, deal with yet more Crème Brûlées, and take the passageway on the right. Follow the upper walkways around, and you'll be dropped to the floor below and forced to deal with Skeletons, Reapers, and more Crème Brûlées.
Once the room is clear take the exit on the eastern side. The next room will be filled with more of the same enemies, so clear the room and return to the top floor via the stairs in the eastern end. Back on the upper levels head for the western end to be confronted by the Iron Giant.
Iron Giant boss battle
You'll be dropped down below again to fight him - his weaknesses are Broadswords, Shields, and Royal Swords, and he has a high Fire resistance, and he'll be accompanied by a few Crème Brûlées. Ignore them and focus your attacks on him, and once you've whittled his health down mop up the remaining enemies.
Exit the room via the stairs behind the door in the north east corner and head for the marker. A few more Crème Brûlées and Skeletons will block your path, and you'll eventually emerge by the balcony which is now a bridge.
As you cross it more Crème Brûlées, Reapers, and Skeletons will emerge. Wipe them out, pass through the circular room on the far side, and follow the corridor. The first corner is safe, but when you approach the second corner the doors will shut and you'll face off against the same assortment of enemies as before. The next corner is more of the same, with the addition of a Lich or two. They're weak to Swords, Guns, Frost and Royal weapons, but resistant to Lightning.
Head down the stairs at the end of the corridor and into the next room. Absorb the elements and mix as many Frost flasks as you can, and make sure everyone's HP and MP are fully restored as it's time for another boss fight.
Need more help? Our Final Fantasy 15 guide and walkthrough can provide tips on main story, as well as the open-world's many quests and activities. Learning how to get AP fast, EXP fast and money or Gil fast will aid you in many optional dungeons and tombs - including how to open and explore their locked doors. There's also plenty of interesting side-quests, too, such as the Scraps of Mystery and Professors Protege frog locations. And if you want to get around easier, you can rent a Chocobo, learn the infinite sprint trick and later in the game, get the flying car Regalia Type F. There's also more to see and do with DLC, such as Episode Gladiolus and Episode Prompto.
Quetzacoatl boss battle
The Quetzacoatl is less problematic than he looks. Use the Warp Point at the end of the room to hit him with a Javelin or Daggers and use Frost to knock the wind out of him. You'll likely get one or two full Armiger charges during the fight, and Prompto's Link attack is a cheap way of dealing a fair amount of damage.
Once he's down pick up the Mythril, head for the exit, and talk to Aranea to begin Chapter 8, which is a short chapter to tick off the list.