Words & Monsters is a free mobile game that teaches the most frequently occurring words for general English and also for several special purposes. Words & Monsters combines patented adaptive technology with fast-paced multiplayer adventure action. At the start, the game adjusts itself to the lexical ability of each player. After about 20 minutes the game will have identified which specific words a player already knows and correlated their vocabulary composition to scores on eight standard proficiency tests including TOEFL, TOEIC and Japan’s kyotsu shiken. The game then teaches each player the most frequently occurring words they do not know, thereby increasing their receptive comprehension. Spaced repetition is employed to build long-term memory retention of newly learned vocabulary. Both the study rehearsals and the game mechanics involve managed uncertainties that are designed to promote emotional attraction to sustain motivation. The game allows for solo and multiplayer activity. When playing with others, a player’s ability level confers no particular advantage; effort and focus are what matter most. This show and tell presentation will look first at how the adaptive technology operates to identify each player’s known and unknown words and then wraps up with a look at the game and the free LMS for teachers. Words & Monsters is available in the App Stores and it is suitable for any level of English ability for ages 8 and up.