Trio Keys Feature

There are various inventory items that are keys -- such as the Skull Key that grants access to Knockturn Alley, or Filch's Keys that enables some snooping in his office. However, this particular guide refers to the Bronze, Silver, and Gold keys, which are a rare set of items known as the Trio Keys.

• Bronze -- Unlocks a random Skill Room. Win the RP'ed mini-game to receive an exp boost. There's a different mini-game for each possible room. Note: Only NEWT-level students can unlock a room associated with an advanced skill.

• Silver -- Activates a cache chest. Win the RP'ed mini-game to unlock it and receive various items.
  

• Gold -- Unlocks a Rune Chamber. Instead of a mini-game, your character faces an obstacle. If they're able to overcome it, you receive a random rune. Info about using runes can be found in the AQ Runes thread in Quests. 

Although these keys can be won from certain events or contests, the primary way to obtain them is by using Shiny Gems (bought in the Wizshop) at the Niffler Sandpit. Details on how that works can be found at the Beast Reserve. You can use as many Trio Keys as you want, but only receive 2 from a Niffler per RPG day. These keys are rare 1-use items and cannot be traded among members.
Bronze and Gold keys are used in the Spiral Tower. Simply RP your character unlocking a random door and your mini-game or obstacle will be triggered. The Silver key is used in the Astronomy Tower, where your character instead tries to unlock a silver chest to trigger the mini-game. A key is used regardless of if you win or lose.

You can use multiple bronze or gold keys in the same thread, though RP-wise your character must exit a completed room, then pick another to unlock. Silver keys can also be used multiple times, as the cache chest will magically reset after each use. These threads can continue through morning and afternoon (if your character skips lunch and has no afternoon obligations / class), but must be concluded before night / dinner.
Key rewards are only given if you win. There are no rewards for losing, except for having fun and increasing your post count. If you're unable to finish a mini-game due to being inactive or RPG time change, your current attempt is voided. You still lose your key and won't receive any rewards. 

• Skill Rooms grant 200 exp to whichever skill it's associated with, and 20 exp to every other skill.

• Cache Chests contain 4 ingredients, 2 game pieces, 1 food item, and a Bubble-Head potion.

• Rune Chambers grant a rune, and 20 exp to all skills. There's a 1/3 chance of receiving a specific rune.