Unstable contains "216-ish" cards (5 basic land, 75 common, 75 uncommon, 46 rare, and 15 mythic rare) and 20 foil tokens, and includes randomly inserted premium versions of all cards. The set explores new areas of Magic game design and continues the tradition of bending the conventional rules of the game in a fun and whimsical way. Unstable was designed to both be drafted alone and be mixed with other sets: according to Mark Rosewater, however, the best experience is probably when it's drafted alone. The expansion symbol is a wrench with an acorn-shaped hole.
The set features 'modern design sensibilities' and is built around a 'cohesive creative vision'. It includes fun legendary creatures that can be utilized in the Commander format and some cards designed for Cube. Like its predecessors, Unstable features 5 full-art basic lands, but borderless instead of black-bordered. Every pack contains one of the five lands unless it is replaced by a Steamflogger Boss, which replaces 1 in every 121 basic lands. The set also features foil tokens, both for tokens produced by cards in the set and for popular tribes outside the set.
The set contains some cards at common which are functionally identical to existing black bordered cards or possibly "blackborderable". These had be included for limited gameplay purposes.
Unstable is only published in the English language.