Thor is a revised version of Wildlife Safari (also known as Loco, Flinke Pinke, and Quandary). As in those versions, there are a number of "stocks" (here, God cards) each with a limited number of identical shares, and players are dealt cards which change the values of specific stocks. On a turn a player plays a value card (with only the last one played counting for each stock) and takes a stock, with a round ending when all the values have been played for a single stock. A number of rounds are played and scores totaled.
Thor differs from the other versions of the game in two respects: it accommodates up to 6 players (by adding an additional stock), and it includes a set of 14 action cards which can be used to affect play.