Serious Sam 4/Gates of Hell

Vesuvious has erupted, and the team needs to escape.

Get back to the car

Exit the boss arena, into the first area. There's only a few space mummies that attack. Ignore the objective marker as that the route it gives is blocked by a door, thus continue to the right and follow the sole path. Enemies are light, although behaded enemies can stand at the top of buildings and snipe with their slow shots.

While proceeding, Professor Kiesel will contact you, asking for five samples of burned aliens, giving a rocket launcher upgrade if done. These locations are marked, and shouldn't be too hard to obtain.

On approach to the first sample (around 50m away), the enemies approach from the left.

After the first sample, the next yard has a sniper rifle in the corner. Enemies will start to become intense, with arachnids attacking. The second sample will be on the left side of the large yard. Continue to the exit on the far end of the area; the instructions from Rodriguez telling not to set your cajones on fire marks a space mummy and arachnid wave, finished off by a large arachnid. There's still more enemies around the corners.

Near the third sample, but protected by more beheaded opponents than normal.

After a tunnel and staircase up, there is a larger number of beheaded enemies, along with an arachnoid and a Harmovore. They are mostly to the right of the entrance, and would be attacking in large numbers here. Defeat the enemies, get the third sample, and continue.

A new enemy appears after descending the stairs, the Draconian Pyromaniac. It's rather armored, but is vulnerable to being hit on the napalm tanks on the back. The large area does have a few more pyromaniacs, along with other minor enemies - eventually leading to a drop with the fourth sample. Drop down to continue.

There is a C4 crate that provides infinite throwable explosives. You'll use them in the next room to destroy barricades, but enemies there will attack shortly after you enter. The barricade on the left leads to the objective, the others towards minor pickups. Further enemies may be easier as you can clean most of them with the infinite C4. When Sam radios with Kenny about his status, the last barricade visible leads to a LIFE gadget. The open path leads to a small arena.

There's two waves in the arena. First includes space mummies, hatcling arachnoids and is finished by an adult arachnoid. The second wave includes Haemovores and a few alduran reptiloids - health kits can be airdropped during the combat, and there's a C4 crate as well. After the second wave is defeated, continue to the gate for a resupply, and a skill point on the left. There is another arena with the final sample, and the exit is on the right.

Escape

You will meet Kenny, and rescue him from being pinned under a statue of Uranus.

Continue down the sole path, you'll quickly encounter combat with a Haemovore. Kenny can provide some cover, although the enemies would mostly target you. Continue to the right - there's a final resupply before the boss arena.

The first wave are the standard space mummies and arachnoids. The second wave has pyromaniacs. This is followed by the Witch-Bride boss fight. She will appear in the air, and will teleport around - when she teleports, follow the she leaves behind for her new location. She may only be damaged when fully visible, or whan the boss meter is orange rather than gray. When she's slain, Sam and Kenny will proceeed to the extraction vehicle.

Secrets

There are 10 secrets.

1. Physically near the first sample. After getting the sniper rifle and the talk about scorp buddies, follow the right-hand wall and look for a broken part of a wall that you can jump unto. Touch the rockets to claim the secret. Entry point is ~1740m from objective, and ~140m from second sample.
2. From the above secret, continue following the wall but avoiding the lava. Eventually you will reach a corner with concrete barricades partially blocking a doorway; around 1620m from objective and 105m from second sample. This contains a L.I.F.E. gadget.
3. To the left of the staircase leading to the third sample (35m from third sample, 1326m from objective), there is a knocked down fence. It leads to a Time Warp object that keeps moving behind the gate. To reach it, pick up the nearby torch on the wall, walk into and out of a nearby fire, then return the torch. Get the Time Warp to claim the secret. As a side note, dropping down from the side can allow you to skip an enemy introduction cutscene.
4. In the first area with the first Pyromanic encounter, there's a rage serum on the right-hand side of the lava pit (1225m away from objective). It's easiest to reach it from the platform's above.
5. In the first area with the first Pyromanic encounter, there's four arches on the left of the lower section filled with lava (about 1210m away from objective). Contains armor.
6. Past these four arches is a miniature lava golem, at the end of the walkway. It's visible as a yellow dot, and is about 1230m from the objective. Shoot it spawns a larger lava golem behind you.
7. After the lava pit, there are rocks to reach higher ground; 1113m from objective, 229m from fourth sample. Jump across the river of lava- there's a L.I.F.E. gadget next to the waterfall.
8. In the area with the fifth sample, there is a kamikazie trap marked by a pill bottle on the left corner. (80m from sample, 865m from objective). The kamikazies are easily destroyed because they're packed together, and will drop pill bottles too - it's best to have a rapid fire weapon against them.
9. After the previous arena containing the fifth sample, turn right. There's a holodecoy past the lava, requiring precision jumping on some rocks.
10. After rescuing kenny, there's a platform near two broken pillars, 335m from the objective. Jump on the pillars to reach the platform. The secret is the companion orb in the lava pool ahead. Shoot it, and the companion orb will follow you for the rest of the level - it is harmless to you, but will harm enemies when it strikes the ground.