Here is the full list of all 46 Lost but Lucid achievements.
Complete Pitfall
Find the red banner in the level Pitfall
Unlock a bonus level with skull collectibles
Finish the main story
Complete darkness dreamscapes
Find the red banner in the level Labyrinth of the Lost
Complete The Courtyard
Find the red banner in the level The Courtyard
Unlock a bonus level with shield collectibles
Find the red banner in the level Veiled Kingdom
Find the red banner in the level River Below
Find the red banner in the level Forest Runner
Find the red banner in the level The Choice
Complete Peaks of Proving
Find the red banner in the level Peaks of Proving
Unlock a bonus level with pyramid collectibles
Complete Gauntlet
Find the fourth red banner in the level Gauntlet
Find the third red banner in the level Gauntlet
Find the second red banner in the level Gauntlet
Find the first red banner in the level Gauntlet
Complete The Birdhouse
Find the red banner in the level The Birdhouse
Unlock a bonus level with mushroom collectibles
Complete Rainbow Maze
Find the red banner in the level One Path Through Darkness
Complete castle dreamscapes
Find the red banner in the level Inner Keep
Find the red banner in the level Tower Topper
Find the red banner in the level The Moat
Find the red banner in the level Outer Ruins
Complete mountain dreamscapes
Find the red banner in the level Canyon Run
Find the red banner in the level Stone Skipper
Find the red banner in the level Rainbow Maze
Unlock a bonus level with star collectibles
Find the red banner on the level Over the Mountain
Find the red banner in the level Cliff Racing
Complete forest dreamscapes
Find the red banner in the level Woodland Temple
Find the red banner in the level Hedge Maze
Find the red banner in the level Verdant Valley
Complete sky dreamscapes
Find the red banner in the level The Fall
Find the red banner in the level The Leap
Begin dream therapy