Winter's Slice Sword Skin
From Guild Wars 2 Wiki
“Double-click to consume.
Seasonal. For sale only during the Wintersday season. Use anytime to upgrade the appearance of a sword. Usable only by sword wielders.
— In-game description
All Wintersday wooden weapons have a wintery snowflake glow as well as a pulsing white branch design. The sword's branch design springs from the sword's hilt. A picture of the sword's glow can be seen here.