In some levels of the Alien and Marine, you can hear the Predator's classic sounds in the background. In some levels as the Alien you can just see the blurry shape of a Predator moving when you enter a new area. There are also Predator Mines laid out in certain areas that can only be reached by Aliens.
As the Alien, you can eventually reach the jungle and exit in a Marine complex. To the far side is a downed ship with "MARLOW" painted on the side. Climb up this ship to find a flat area of land on the other side of the electrified fence. Moving too far, however, will result in an instant death.
In several levels are red gas canisters with a small pilot light on them. These can be pushed easily by walking into them. Get behind the smart gun and push it as close as possible, then strike it once with a heavy attack (should be a tail strike). You will have a small amount of time to flee before it explodes, disabling the smart gun
Heal or regenerate 30 blocks of health in Survivor.
Alien vs Predator (30 points)
Create a new species.
Breaking Quarantine (15 points)
Escape from the Research Lab.
Breaking and Entering (15 points)
Find a way into the Research Lab.
Club hopper (15 points)
Survive The 'Party' at The Club.
Come to Mama (15 points)
Liberate the Matriarch.
Elite Sniper (15 points)
Kill 10 enemies with head shots from the scoped rifle.
Exit Strategy (15 points)
Escape from C-Block.
Extinction Agenda (30 points)
Destroy the Abomination.
Eyes of The Demon (15 points)
Retrieve the ancient mask.
Fallen Comrade (15 points)
Find the Youngbloods in the Jungle.
Fortune and Glory (15 points)
Find all 45 Predator trophy belts.
Game Over, Man! (30 points)
Beat all three Campaigns.
Get to The Chopper! (30 points)
Recover Weyland's datapad.
Grim Reaper (15 points)
Harvest all available civilians in the Alien Campaign.
Grunt Hunt (15 points)
Wipe out all of the Marines in the Colony.
Gunslinger (30 points)
Kill 30 enemies with the pistol.
I Like to Keep This Handy (15 points)
Kill 2 enemies with one shot with the shotgun.
I Will Never Leave You... (15 points)
It Uses The Jungle (15 points)
Find a way through Gateway.
Killer Instinct (15 points)
Win your first Ranked Match in standard Deathmatch mode.
Let's Rock! (15 points)
Kill 5 enemies with one burst from the smartgun.
Matter of Honor (15 points)
Discover the Elite Predator's fate.
Not Bad for A Human (50 points)
Earn all achievements.
One Big Bug (15 points)
Defeat the Praetorian.
Persecution Complex (15 points)
Achieve Persecutor status more than once in any Ranked Match.
Quite A Specimen (15 points)
Destroy all 50 Royal Jelly Containers.
Real Nasty Habit (50 points)
Get 18060 XP in Ranked Matches.
Reclaimer (15 points)
Retrieve the second artifact.
Regicide (15 points)
Defeat the Matriarch.
Scatter Shot (15 points)
As a team, kill 20 enemies in under 60 seconds in a Survivor match..
Serial Killer (30 points)
Win 10 Ranked Matches in any Deathmatch mode.
Spin Doctor (15 points)
Kill two enemies with one throw of the Battle Disc.
Stay Frosty (15 points) -Beat Marine Campaign on Hard difficulty setting. I Admire its Purity (15 points) -Beat Alien Campaign on Hard difficulty setting. It Ain't No Man (15 points) -Beat Predator Campaign on Hard difficulty setting. I LOVE the Corps! (30 points) -Beat Marine Campaign on Nightmare difficulty setting. Magnificent, Isn't It? (30 points) -Beat Alien Campaign on Nightmare difficulty setting. One Ugly Mother (30 points) -Beat Predator Campaign on Nightmare difficulty setting. Harsh Language (15 points)
Discover all 67 Audio Diaries.
Stick Around (15 points)
Kill 20 enemies with the Combi Stick.
The Six Pack (30 points)
Play with six friends in a Ranked Match.
The Uninfected (30 points)
Finish a Ranked Infestation match as the only remaining prey.
Under Pressure (15 points)
Solve the riddle of the Ruins.
Very Tough Hombre (15 points)
Kill 10 enemies in a row without dying in a Ranked Match.
Welcome to The Party (30 points)
Get 6000 XP in Ranked Matches.
Welcome to The War (15 points)
Play and complete your first Ranked Match in standard Deathmatch mode.
As Alien in level 3, the Queen will tell you to get to the bottom of a shaft with a giant fan at the top. As you get near it, another Xenomorph will be swept away and blown into the fan. If you use your Focus, you can see two vents on the opposite wall. select either of them and you can safely jump to it despite the power of the fan. As you go, you will find more vents to hide in. Use them to make your way down.