Celesta's Slots is a slots-type game of chance. You receive one roll per day.
It is only available on the iOS app.
As of 3/2017, Daily Spin is now available in FB and web3/4 versions of CA in the Battle News area.
List of possible prizes
Prizes were updated on 8 March, 2017. Old prizes had mostly items of very little value anymore, with update bringing in lots of valuable prizes.
Chest images have been changed earlier. Gold and Epic chests are still easy to recognise, but former Bronze and Silver chests are now both silvery, just one is dim while other is bright.
Also, it doesn't seem to matter whether you get two or three of the same chest. Rewards depend only on whether you get at least two of a chest, and then which chest it is.