Underground Laboratory/R&D Access
At the start of the game, poisonous gas permeates the whole area, therefore decreasing your Vitality Gauge until you die. Fortunately there are some scattered mini-Green Orbs around the area. There is also an orb statue from which you can destroy to obtain your blue orb fragment. After entering the area, it's time for you to hunt one of the most annoying demons in this series- the Cutlass. Unfortunately for you Dante does not have a Devil Bringer, meaning you can't snatch to stun enemies. Therefore another effective method for players was to use Trickster Style and Coyote-A to Charge Shot 3 and Lucifer , orRebellion and Sword Master Style if you prefer close-quarter combat. After defeating them simply head straight to the Game Room.
Game Room
An easy way to defeat all of the Gladii there is to use Lucifer and the styles Trickster and/or Sword Master . Simply perform Pin-Up, then Splash and then Discipline all the way to victory. A sure SSS rank will go. Simply head to the door to the Containment Room after defeating all of the enemies.
Containment Room
Same strategy, but this time it will be a much harder fight because Bianco and Alto Angelos appear in the area. After defeating the enemies simply head straight outside the location.
Forris Falls
Simply get the Green orb, destroy all of the barrels to get Red Orbs. There is also a Blue Orb fragment located in the uppermost level of the area. You can get this by performing Stinger then Sky Star (Note: Perform this if you haven't obtained the orb before). Enter the door.
Angel Creation
This is the hardest part of the battle here, for you will be encountering a lot of Bianco and Alto Angelos here. One of the most effective way to finish the area quickly and to gain a SSS rank for a good play is to use all of the styles to the maximum level (mixing all the styles including heavy sword and gun play, especially when playing on harder modes). Also remember that you can kill them almost instantly if you wait for the Alto Angelo to summon its massive energy ball. Shoot it with Coyote-A and then it will scatter causing massive killing spree around the area and a quick SSS rank. There are also Red Orbs there. Head straight to the exit.
Grand Hall
Collect all Red Orbs if you want.
Fortuna Castle Gate
Simply head out. There you will encounter a new enemy, the Basilisk. Be careful with this devil hound because its attacking ability of shooting fireballs is not a joke. Use Royal Guard Style if you want to play safe or Trickster Style if you want to play cool. A Stinger three times will kill them instantly. After defeating them simply head out by climbing through the mountain. An arc can be seen there. Also Secret Mission 11 is located there. On the second part of the area more Basilisks will appear. Kill them instantly.
Second Mining Area
Head down to the exit or get the blue orb fragment first located at the south part of the map. You can see a wooden door in front of the entrance where Nero enters. A Red Orb statue is also located there. Simply exit to battle the Boss.
Boss
Berial's fight is surely an enjoyable (yet a little bit long) one. It's difficulty level (through all the game difficulties) just ranges from medium to normal, so you don't have to be afraid of battling him. Here you can practice your Pandora shooting skills.
A good strategy for defeating Berial for rookies is to shoot it with PF398: Revenge for four to six times (although sometimes more shots are needed in harder modes, since the difficulty level only affects to how strong Berial's flame armors are). After extinguishing the flames around his body, he can still move and attack you, although he is more vulnerable now to some powered attacks like Kick 13 or Over Drive. After you have knocked him down, switch to Sword Master style, then Gilgamesh's Real Impact will surely kill him instantly (on Human mode) or decrease his life bar to almost 3/4 (on harder modes). After decreasing his life bar, he will attack more visciously. Evading his volcano fire attacks will do, but he will charge a leaping sword attack, so be careful of running. After you defeat him, there is cutscene of Berial being taunted by Dante to retreat or fight back, but Berial says he will never retreat again and performs a kimkaze move, which Dante simply blocks by shooting. Afterwards Dante destroys the Hell Gate with the use of his new Devil Arm, Lucifer.
Trivia
- Most professional gamers and even experienced ones say that Lucifer is a very useless weapon against Berial.
- The mission title Inferno refers to Dante's way towards Berial, the Conqueror of Fire Hell.