Heroes of Newerth is the latest online game to integrate a free-to-play strand, and this time it's one with ties to another online success story, League of Legends.

Both can trace their lineage back to Defense of the Ancients, an eight-year-old modification for Warcraft III.

The two will also have an eye on DOTA 2, currently in production at Valve ( Left 4 Dead, Portal, Half-Life).

League of Legends makes money by allowing players to buy characters, costumes, and in-game items.

Its global popularity was illustrated when Chinese web firm Tencent Holdings bought a major stake in creator Riot Games.

When Valve's own multiplayer shooter Team Fortress 2 adopted a similar approach in June, some veteran players reacted by banning incoming freeloaders from their sessions.

Heroes of Newerth, perhaps mindful of this as well as newcomers' desire for inclusion, is instituting a verification process that rewards good behavior and monetary investment.

Once new players are proven mindful of gameplay etiquette, or have made a purchase from the HoN marketplace, they'll gain Verified status - though intentionally messing up someone else's game can see that status removed.