What Wardrobe does
Wardrobe is an account-wide appearance collection. Once you unlock an appearance, every character on the account can apply it, permanently and repeatedly, without hunting down the same rare drop again.
How to access it
Open Wardrobe from the main menu's Features submenu. The window lists everything you've already unlocked on the left, with the unlock and apply steps on the right.
Unlock, then apply
Drop an eligible item onto Add an appearance and sacrifice it to unlock that look permanently. Previewing an unlocked appearance is free and does not require any item or scroll.
Applying an unlocked appearance to a piece of equipment consumes one Scroll of Transmutation (item 31005, 25 Perin from the Perin Shop). The target keeps its own stats, upgrade stage and Rarity; only its appearance changes.
Limitations
Sacrificing an item to unlock its appearance destroys that item. The unlock itself is permanent and reusable — you are not spending it again each time you apply the look.