Exclusive to: 
Only during the Event:
Year of the Clockwork Knight
“Ignore the neigh-sayers.”
–Wilson
“It definitely matches the head.”
–Willow
“These garments are indicative of royal status.”
–Wickerbottom
“I suppose it goes with the bossy horse head.”
–Maxwell
“Röbust it is nöt, but lövely? Möst assuredly.”
–Wigfrid
“It must be for parties.”
–Webber
“Hmm. Think it works together with the mask.”
–Winona
“A princess must dress for success!”
–Wortox
“Someone ponied up for this outfit.”
–Walter
“A rather fancy outfit for a horse.”
–Wanda
Princess Costume and Princess Mask are armors dropped from Briar Wolves that spawns when player goes Stage the first time after making offer on Clockwork Knight Shrine, or from Briar Wolves that spawns on Set Piece with Overgrown Statue.
Full set of Princess Costume (Princess Costume and Princess Mask) will spawn 4 different Gilded Knights that will be passive to players will full set, will following them tring to make stand always on 4 sides around the player and will try to protect player. After Gilded Knights die, they will respawn after 3 days when the set is equipped.
Wearing the Princess Costume set decreases the Luck by 1.
Princess Mask
“I dunno... I kinda like it.”
–Willow
“Sometime Wolfgang want to try royal treatment.”
–Wolfgang
“There's a lonliness in her expression.”
–Wendy
“That's kinda pretty.”
–Woodie
“She looks a little bossy.”
–Maxwell
“Lacking a warriör's visage, she yet cömmands.”
–Wigfrid
“That's a big party hat!”
–Webber
“She looks like someone who gets her way.”
–Warly
“There's more to this pony princess mask.”
–Winona
“A mask for a phony pony!”
–Wortox
“Me already princess.”
–Wurt
“Her Royal High-neighs!”
–Walter
“She has an attitude about her.”
–Wanda
Assets
Princess Costume Equipped