Part 28

Vamp Boss Fight: Vamp attacks with knives and a melee combo. He regenerates due to his nanomachines. To defeat him, equip the syringes given by Naomi. Get close enough to perform a CQC chokehold on Vamp and use the syringes. This will deplete his health and end this phase of the fight. Using lethal weapons on Vamp before the syringe does not count as a kill for a no-kill playthrough.

Suicide Gekkos: After Vamp is dealt with, Raiden appears. Your objective is to protect the area from Suicide Gekkos that attempt to detonate. Use Crying Wolf's railgun (hold R1 in aiming mode until the charge meter is full) to destroy the Gekkos in one shot. Stay near Metal Gear Rex for cover, but move when Otacon warns of attacks from above. You must destroy approximately twenty Gekkos.

Escape the Underground Base: Once the Gekkos are cleared, you will pilot Metal Gear Rex to escape the underground base. Rex has several attacks: Gatling gun, AT missiles, FE Laser, a charge (X), and a kicking combo (R1 when not aiming). Avoid being near Gekkos when they explode, as this deals significant damage. You can either destroy them from a distance with the machine gun or charge through them before they detonate. The goal is to reach the exit within the five-minute time limit or before Rex's health depletes. You can earn Drebin Points by defeating the endless swarm of Gekkos.

Metal Gear Ray Boss Fight: You will face Metal Gear Ray while piloting Metal Gear Rex. Rex's arsenal includes the Gatling gun, AT missiles, FE Laser, charge, and kick combo. It's recommended to use Rex's kicking combo followed by a special Triangle attack when close to Ray. Use missiles to stop Ray's charges and the Gatling gun to destroy its missiles. Avoid using the FE Laser as it leaves you vulnerable. Ray's main attacks are a water cannon and a missile barrage, which it uses when given space. To win, stay as close to Ray as possible to limit its attack options to charging and tackling.