Valve has used Dota 2 to test all sorts of interesting doodads for professional gaming, from selling tickets to watch matches in an oh-so-slick spectator system to, heck, hosting a huge annual tournament. As third tourney approaches, Valve is launching The International Interactive Compendium, a social-y thing which'll let fans predict results together, win prizes, and vote on things like who plays in the all-star game.

Valve describes the Compendium as "a virtual book that will keep you fully up to date with the state of The International." It'll track matches and all that, and you can predict results then compare with your chums to show off. Compendium owners get to vote on who plays in The International 3's all-star match too, and who gets awards.

Owners can receive items whilst watching matches, as with pennants and tournament tickets, and it comes with a fancy courier Smeevil which unlocks shiny extra customisation bits as you watch.

The Compendium also raises the stakes for TI3, as Valve will add 25% of its revenue to the already-impressive prize pot of $1.6 million. Gosh, teams will fight awfully hard for a share of that.

You can buy the Compendium now from the Dota 2 store for $9.99. Check out its official info page for more on this weird and not-quite-properly-explained thing.