Seasonal Sales are limited-time sales that align to a new ‘season’ of Gods Unchained. Seasons introduce new expansion sets. For example: the expansion sets Trial of the Gods and Divine Order are both part of Season 1: Champions Rise. A seasonal sale runs for a limited time, during which players can purchase first edition expansion card packs directly from the Gods Unchained website.
A portion of seasonal card packs is always reserved for rewards and giveaways so they can be won by players after the sale has ended (as has happened in Weekend Ranked tournaments).