The Story of Kog'Maw
The Void produces creatures of hunger and destruction — purposeful, directed, malevolent. Kog'Maw is the exception. Belched from a rotting Void incursion in the wastelands of Icathia, he emerged with the curiosity of a child and the appetite of a natural disaster. He wants to understand the world around him, and his primary means of investigation is tasting it.
This is more destructive than it sounds. Kog'Maw's digestive acid dissolves nearly any material, and his enthusiastic attempts to sample village huts, fortifications, and unsuspecting livestock have left trails of disaster across wherever he wanders. He doesn't mean any harm — he genuinely doesn't understand that eating someone's house is a problem. He's just curious.
The Void's influence is seeping deeper into Kog'Maw over time. Malzahar, the Prophet of the Void, sees in this creature a tool — a living weapon of consumption to deploy against Runeterra's defenses. The innocence that currently characterizes Kog'Maw won't survive that influence forever. For now, he wanders with the delight of a being experiencing the world for the first time, leaving dissolved everything in his wake and entirely failing to understand why everyone keeps screaming.