The Queen Plaga resembles a giant plant-like organism. It is immobile and consists of a large fleshy bulb that opens like a flower, surrounded by many tentacles that anchor it in place. It continuously spawns Plagas and was well protected by the Los Illuminados.
During the events of the Kennedy Report, Leon S. Kennedy's attempts to rescue Ashley Graham were impeded by Salazar, who sacrificed himself and one of his Verdugo bodyguards to the Queen Plaga, allowing them to be assimilated into the giant organism. A large head similar to the Verdugo's emerged from the Queen's bulb attached to a long, tentacular neck, atop which Salazar's own body had been fused to. Leon was able to dodge the monster's attacks and kill it by attacking Salazar himself when he revealed himself.
When Leon fought against it, the Queen Plaga used its many vine-like tentacles to whip at him and pick him up and throw him. It also constantly spawned C-type Plagas to attack Leon and the large mutant head could even split open down the middle, revealing a terrifying maw that could've snapped Leon in half.
A large, tumour-like eye on the creature's head served as a weak spot and shooting it would cause Salazar to reveal himself. Shooting Salazar, who had merged with the Queen, was what finally killed it.