The Keys of Harmony are key items in 34DOOM. They are used to unlock specific doors or mechanisms. They're from the world of Equestria and have been created by the six ponies of Harmony in order to help the Grand Sage's chosen ones in their progression.
There are 6 keys:
Loyalty key : a red lightning, Rainbow Dash's element
Laughter key : a blue balloon, Pinkie Pie's element
Honesty key : an orange apple, Applejack's element
Generosity key : a purple gemstone, Rarity's element
Kindness key : a pink butterfly, Fluttershy's element
Magic key : a pink star, Twilight Sparkle's element
There is one lock for each key. But there is also locks that require more than one key:
Locks needing 3 winged ponies need: Loyalty, Kindness et Magic
Locks needing 2 earth ponies need: Honesty and Laughter
Locks needing 2 unicorn ponies need: Magic and GGenerosity
Locks needing the complete Harmony need the 6 keys