The Queen Plaga is a boss fought in the Tower summit at the end of "Chapter 4-4". It has two body sections with their own hitpoints - the tentacles are worth 200 and respawn, while the body (with Salazar in it) is worth 3000. The body has to be completely depleted in order to defeat the boss. On the bottom floor, there are up to three Plaga Cs walking about. If any are killed, more spawn to replace them indefinitely until the end of the fight.
If a Rocket Launcher is aimed and fired at Salazar's body, a short cutscene will play where he is hit directly by the rocket and the whole monster dies instantly. Upon defeat, the Queen Plaga leave behind 50,000₧ (and the plaga despawn at the lower level).
The tentacles are capable of using the "Tentacle bashing" and "Throw grab" moves. "Throw grab" will send Leon to the lower level of the room. The tentacles retreat back into the wall after they sustain 200 damage. After a set amount of time, they will come back out.
The body can use the "Crush" and "Instant death bite" attacks. It has one large eye which is where it can be damaged. Once it has taken a certain amount of damage it will become limp and not move while the bone like cage protecting Salazar's body opens. After a short set time the cage closes and the head wakes back up. Salazar's body will be defenseless and simply needs to take a certain amount of damage for the fight to be won.
Stay at the side near his arms. Not in the middle. When he goes for the bite move just stay where you are and he will be unable to bite you. This is useful because his bite move will rip Leon apart, causing an instant death. If you stay to one side and shoot the tentacle, you cannot be hit by any of Salazar's attacks. He cannot reach you (until the tentacle comes back).
There is no need to get at the lower floor during the fight unless you run out of ammo.
40-45 damage points are needed to expose Salazar's body.
Salazar has around 220 hit points. It would take 17 un-upgraded Broken Butterfly shots to kill him. Head shots have no damage amplification.
The Mine Thrower and the Broken Butterfly can also be used to dispose of this boss. Be sure that these two weapons are well upgraded before using these tricks to beat him: Shoot the giant Verdugo head with the Mine Thrower. It should disappear after one shot, leaving the player the chance to attack Salazar with the magnum. If the player runs out of ammo, use the Semi-auto Rifle.
If a rocket launcher is fired and hits one of his stationary tentacles, he will comment slyly and take little notice.