White Owl is one of the three skins released under the Yeti's Mountain part of the Winter offer. It could be purchased using game coins on an individual basis in mid November 2017.
White Owl could be purchased in the Skins Shop under the ‘Winter’ tab for 690 coins. It was available for a limited time and may not be available for purchase in the future.
Details of this offer can vary depending on location, platform or time.
Note: The Yeti's Mountain sub-offer with the White Owl skin was released again for a limited time in late November to early December 2018. The price for White Owl remained the same at 690 coins.