Secret Room

Secret Rooms, occasionally called Secret Chambers, are a feature that was added to the game in PMU7. They appear in set floors throughout several dungeons and can be rarely found and accessed by stepping onto a hidden stairs tile.

Secret Rooms often rewards players with a varying amount of Deluxe Boxes that can give Common or Rare items when opened at Xatu's Appraisal. However, Secret Rooms may also allow players to spawn rare, exclusive Pokémon with Honey.

Location
The following below lists the Dungeons that contains Secret Rooms and their corresponding information:

Exbel

 * Gritty Hollow - 2 Boxes
 * Far Thunderstorm Forest - 4 Boxes
 * Harmonic Tower - 3 Boxes (50F-74F), 1 Box (75F-98F), Bagon
 * Honeydrop Meadow - Scyther (Dawn)/Pinsir (Dusk)
 * Island Garden - 2 Boxes
 * Loch Lenile Cavern - Red Moon Spring (11F-19F), 2 Boxes
 * Sentimental Aquifer - ???
 * Sentimental Aquifer Depths - ???
 * Southern Sea - 4 Boxes
 * Thunderstorm Forest - 4 Boxes

Winden

 * Mt. Stormhold - ???
 * Sky Fortress/Fairy Path - ???
 * Sky Fortress/Fire Path - ???
 * Sky Fortress/Ice Path - ???
 * Sky Fortress/Electric Path - ???
 * Snowveil Den - ???
 * Winden Forest - ???

Pokémon
In certain secret rooms it is possible to spawn Pokemon with Honey. The Pokémon that spawn in these rooms are often rare Pokémon only in these areas. The Pokémon that spawn in these rooms are as follows:
 * Scyther - Honeydrop Meadow (Dawn Only)
 * Pinsir - Honeydrop Meadow (Dusk Only)
 * Combee - Honeydrop Meadow
 * Vullaby - Undercity Catacombs

In Sunrise Temple, the player can obtain a Larvesta egg after going through a puzzle.

Red Moon Springs
Red Moon Spring is a special secret room that was added to Loch Lenile Cavern. It serves a special purpose and a different layout then the common Secret Room. Instead of the common Deluxe Boxes or Honey Spawns that are found in other Secret Rooms, you regenerate Fossil Pokémon using Fossils.

Pokemon
The Fossils that can be resurrected in Red Moon Springs are as follows:
 * Helix Fossil (Omanyte) - Tanren Chambers/Water
 * Dome Fossil (Kabuto) - Crystal Ruins
 * Old Amber (Aerodactyl) - Mt. Skylift
 * Claw Fossil (Anorith) - Tanren Chambers/Bug
 * Root Fossil (Lileep) - Tanren Chambers/Grass
 * Armor Fossil (Shieldon) - Tanren Chambers/Steel
 * Skull Fossil (Cranidos) - Tanren Chambers/Rock
 * Plume Fossil (Archen) - Tanren Chambers/Fighting
 * Jaw Fossil (Tyrunt) - Dragon's Descent/Dragon's Descent Depths

Recruitment
When you summon the Pokémon via Fossil, the Pokémon will be at Level 25 recruitment rate of 100%.

Trivia

 * Secret Rooms only appear in randomly-generated dungeons. Fixed dungeons such as Friendship Forest will never have Secret Rooms.