Titan

Titans were creatures that showed up after the creation of Tethys. These beings were of legendary size, some even up to a kilometer or two in height. They were very powerful and fought against the the First Gods during the First Age, The Titan War. The Titans ultimately lost, most were imprisoned, others were destroyed. Their will lives on as Icons, Will of Titans and some can be "visited" like Atlas, the Betrayer. Also, each Titan has its own Constellation.

First World Theory

During the First World, there weren't any Titans. The Ancestors of Giants called All-Father and his Jotunn were immense in size but really were different species. Once the world broke and was remade, the once heroes turned gods (First Gods) found themselves in a war against creatures of unknown origins. It seemed like they are birthed once a new world is created. Maybe they were the original Titans from First World and they woke up again to fight against interlopers - gods.

List of Titans