Mister Mushroom

Mister Mushroom is a talking mushroom found through various locations in Hallownest after the player has progressed past a certain point. His babbles can be heard from a distance, guiding the player to his location.

Finding him in all seven locations and ending the game rewards the Passing of the Age achievement and a secret cutscene after the player has beaten the game.

To understand what he says, the player must equip the Spore Shroom charm, otherwise he'll speak gibberish and won't move to the next location.

Riddle Tablet
The Riddle Tablet is a glowing glyph in a secret room at the bottom right corner of Kingdom's Edge. When the player reads it with the Spore Shroom charm equipped, the tablet reveals a poem, which gives hints to the locations where Mister Mushroom can be found.

Locations
Defeating all 3 Dreamers will trigger Mister Mushroom's appearance. He can be found in 7 different locations. Each one must be visited in the order described on the Riddle Tablet.

Trivia

 * Mr. Mushroom's first dialogue is a likely reference to Team Cherry's entry 'Hungry Knight' for the Ludum Dare Game Jam 27, in which they first used the player character that became The Knight. In the game, the player has to keep feeding on cherries dropped by enemies and kill three bosses (whose icons look similar the Dreamers') to resurrect a friend.

Мистер Гриб