In March 2004 DotA version 4.0a was released and Roshan was introduced. Roshan is a neutral monster, similar to Baron Nashor in LoL (notice the anagram?), who oddly enough was named after Guinsoo's bowling ball. The introduction of the 5.xx DotA series brought a lot to the game. This series contained the first stabilized competitive mode, and with that the emergence of organized competitions.
The first league, Clan TDA (The DotA Allstars), was created in April 2004. Its popularity was mostly spread through the site DotA-Allstars dot com, which was created on October 14th, 2004 by TDA member Pendragon (also the same Pendragon on Riot's staff). It became DotA's official website and by 2010 was hitting 1 million visitors every month and 1 million page views every day. Sadly Pendragon took down the site in July of 2010 and the official DotA site was moved to PlayDotA.com. In 2010 the number of people that play DotA was estimated to be 15 million worldwide. Had this been a commercial game it would have been a smash hit. DotA has been said to be the most popular mod of all time, even beating out Half-Life's famous mod Counterstrike.
In October 2004 Guinsoo also brought on fellow Clan TDA members IceFrog and Neichus to help with the massive workload. During this time version 5.84c was created, which was considered one of the best versions of the game. To this day you can still find this version in Chinese cybercafes. It's worth mentioning 5.84c wasn't actually released by Guinsoo due to a bug in 5.84b, but by a Russian modder by the name of True.Rus.
In 2005 Blizzard hosted a DotA tournament at its very first Blizzcon. Blizzard was one of the biggest game companies in the world, and for them to feature DotA at their convention showed just how far the mod had come. DotA now had the recognition from Blizzard it deserved, and was well-received at the convention.
However, the winds of change were blowing as Guinsoo announced he would be stepping down as lead developer. On February 28th 2005 developers Neichus and Icefrog took over; with Neichus filling the position of lead developer. However, after several versions and a lot of new heroes Neichus decided to step down and IceFrog took over as lead developer. IceFrog is largely credited by the DotA community for making the game what it is today. His modifications focused on balancing heroes as he found that too many of them were unbalanced; think of these as the nerfs and buffs every week in League of Legends that help keep champions in check. These modifications paved the way for DotA as a serious eSport, and DotA found the most growth in players during IceFrog's reign.
Check back next week to see the MOBA genre commercialized!