nearest thing would be the "game" plugin www.moodle.org/plugins
simple snake, crosswords, and a few other basic generic games.
"badges" and "level up" plugins, might be of interest to you.
never messed with it but keep seeing poodle and ways they have integrated different things into moodle.
suggest start copy/pasting from a module (activity / resource) ((www.yoursite.com/moodle/mod)) and building off from that. and slowly adding / creating different types of plugins moodle uses. from grade/quizzes, to other. pending on how tightly you want integrate things into moodle.
groups / grouping, at categories for courses then at course level, and then at enrollment level, and then per activity / resource might be something worth while for creating "clans" there is also "cohorts" that is mixed into it.
pending on how integrated game is. you might look at a new "course format" and then turning on "meta courses" within "site admin menu" and then creating some additional blocks and/or using blocks already that come with moodle. for chat or like.
the completion and availability API's turn them on in "site admin menu" can bring in some basic stuff. but not to overly complex data sets. for setting up quests and like in larger detail. it might be good enough for simple basic game and handling stats. and levels. if going this route... you are looking at more of either "hosted" on your servers, or publishing course into moodle.net so all your completion and availability settings get passed on.