Del Lago is a large aquatic creature that appears as a boss in Resident Evil 4. It is a bio-organic weapon created by the terrorist cult Los Illuminados and was produced by manipulating the genes of a salamander and infecting the creature with a Plaga parasite. The creature grew to tremendous size and made its home in a lake not far from Valdelobos, where the Illuminados were based. The cult would use the Lago to dispose of evidence, casting the bodies of outsiders and interlopers into the lake for the monster to devour.
Leon S. Kennedy of the U.S. Secret Service investigated the lake during his mission to rescue Ashley Graham, the then-president's daughter. He operated a small motorboat and fought the Lago creature by throwing harpoons at it whenever it surfaced. A mooring rope on the boat got snagged by the Lago and the creature pulled the boat with it as it swam around the lake. When Leon killed the Lago, the monster descended to the bottom of the lake and would have dragged Leon down with it had the agent not used his combat knife to cut the mooring rope that got tangled around his leg.