What are Limited Time Offers?
Offers are sets of various resources (orbs, lock picks, gems, etc.) offered at profitable prices. You can buy them for real money via plastic card by tapping on an old thief icon in the bottom of your dungeon. Offers are renewed every 72 hours.
There are also so-called One Time Offers, that may pop up during the gameplay when you most need them. If you reject buying one of them, it will not be shown again.