Sand Empire runs through the month of June. It is the Seasonal Event associated with summer. You may play the event on Normal or Advanced. The successful completion of the event's quests awards each of the trainer heroes and ascension materials. There are also 6 heroes associated with the event which you may pull via the Seasonal Summon. In 2019 it was held from June 24th through July 7th.
Sand Empire Heroes
|3* Heroes||4* Heroes||5* Heroes|
|Arman (Holy)||Gafar (Dark)||Rana (Holy)|
|Hisan (Nature)||Jabbar (Dark)||Yunan (Nature)|
Cap has put together a list of what you can expect from each stage: