Follow the catacombs towards Oktyabrskaya - part 2 | Chapter 18: Undercity Metro: LL Guide
Last update: 11 May 2016
Go straight ahead to find a corpse with supplies on it. After you reach a not-so-stable bridge, you will encounter, for the first time, a monster called the Big Momma. The entire wooden structure will collapse, as a result of which, you and the best both land in the bottom "arena".
The most important piece of information, in connection with the (first) battle with Big Momma is that, although you don't really have to waist ammo or grenades on attacking it. Instead, take cover behind large pillars like the one in the above screenshot. The mutant will regularly perform charges at you and take damage while smashing the elements of the surroundings.
Continue avoiding Big Momma and sprint from on pillar to another. Wait there until the monster attacks with its charge. Repeat this maneuver until the moment when all the pillars are destroyed. The beast should then ram through one of the walls and leave the arena, and open a passage at the same time.
Take the tunnel and find a corpse on your way, along with a machine gun and a supply crate. After you reach another large cave, you will have to fight another battle with the Big Momma.
At the beginning of this battle, focus on eliminating mutants as quickly s possible, thanks to which the monsters will no longer interfere.
Phase two of the encounter is very similar to the previous instance so, you need to position yourself near the columns and wooden barricades to encourage the monster, in a way, to charge at you and take damage as a result of ramming into the obstacles.
Keep running all around the arena and position yourself behind columns and barricades. Start attacking the monster only after big momma destroys all of the nearby obstacles. The good news is that the monster should already be exhausted by now, so a few shots with a good weapon, or a grenade, should do the trick.