The Magic: the Gathering (MTG) set Theros (THS) was released on Sep 27th, 2013. It includes 13 token cards.
Theros is an expansion set in the Theros block. An expansion set in Magic: The Gathering is a pool of cards released together and designed for play in the same environment. Standard cards and tokens in a set can be obtained at random through booster packs. Sometimes a set will contain promo tokens that are given away as prizes at Friday Night Magic (FNM) or special pre-release events.