Gatekeepers, or toll birds, are non-playable characters that grant access to areas in An Untitled Story. They must be paid crystals to open the toll gates. The Hatch powerup is required to talk to them, otherwise they will ignore the player.
There are four toll birds in the game: one in NightWalk, one in Farfall, one in FireCage and one in SkyLands. Only the one in NightWalk must be paid to beat the game on regular/casual. In difficult you must also do the one in Firecage, and on masterful you must do all but the one in SkyLands