The Ogre's Swamp is a wetland area off the Forgotten Forest Glade. It is home to a single Ogre that gives the marsh it's name. The swamp contains the shadow well to find Thermite.
The entrance is a door in a tree with a large target over it. The door can be opened by using Snare to throw Magmites at the target, and detonating them with Chilla's Ice Spike ability.