Gnezdo (Marco)

Chapter: C3 · Lanshiang: Poisawan, the Stilt Houses and the Medical Center
Where: 3-3 Poisawan Inner Area, upstairs, right after the Iluzija

Weak point

The queen: the large insect flying apart from the swarm

Marco becomes a chrysalid and a Gnezdo hatches: a swarm of insects around a queen. Killing the queen is the only way. If the swarm catches you, it drains your health and you have to shake the stick.

Reward

Marco's C4 (key item). Unlike ordinary Gnezdo, it does not drop the 2,500 SP Queen (Silver).

Breakout and Defense Lv3 help against the swarm's grab.

Step by step

Shoot the swarm with the shotgun to scatter it and expose the queen.
Empty the shotgun into the queen from medium range: that's the main method. This chapter only has fixed 40mm Explosive Rounds; if a crate happened to give you 40mm Acid Rounds, use them here: they're especially effective against the Gnezdo.
Back off or slide to avoid the swarm; in co-op, one player scatters and the other finishes the queen.
Collect the 5 crates around the room and Marco's C4 to blast the doors.