The Legendary Keyblades are Weapons with powers that only their owner can use.
There are some keyblades that serve for the shadows
The list of secret keyblades:
StickBlade belongs to Stickman (Stickman will get the stickblade in a new season)
WiseBlade belongs to Shurow
Xblade belongs to "X"
DZeroblade belongs to Dororo
Nexus Keyblade belongs to Carlos Mtz2
TechBlade belongs to Gary
MaesltromBlade belongs to Makuta
ShadowBlade belongs to Makuta
MaxBlade belongs to Max
The Ultimate Keyblade of Shadows belonged to Makuta before he used all it's power to transform into the Ultimate Makuta.
The Ultimate Darkness vanquisher belongs to Stickman (He will get this in the true final episode of the Stickman Series.)
Phantom S Keyblade belongs to Stickman. (This keyblade is a transformation keyblade. This one allows Stickman to transform into his rhythm counterpart; Phantom S.)
The Royal King Keyblade belongs to Stickman. (This one is also a transformation keyblade. This one allows Stickman to transform into his royal alicorn form.)
Wikia Signature belongs to Shurow.
Friendship Keyblade Belongs to Stickman. (This one is one of the keys unlocking the true past of Stickman.)
Bird's Eye View is Jewel's keyblade. (This one is Jewel's other main method of attacking, and is used the most in battle. She can also use this to transform into her rhythm thief counterpart; Flying Samba.)
Blazing Wind is Skye's keyblade.