From Dota 2 Wiki
The All-Hero Challenge is an in-game achievement that can be obtained by winning a match with every hero. Doing so will earn the player a trophy in the Gallery of Triumphs.
- The current hero will be marked with a blue icon on the hero selection screen.
- Statistics are provided on the average number of matches it took players worldwide to win with each hero, and to complete the entire challenge.
- The challenge can be completed an infinite number of times.
- The challenge can only be completed in matchmaking, player vs player game modes.
- When a player abandons, the current game may not count towards the challenge.
- When a player is in low priority, any matches made won't count in the challenge.
- If poor network conditions are detected, the game won't count towards the challenge.
- Bot matches won't count towards the challenge.
- Players are assigned a new hero after each win.
- The order of the heroes is a cyclical list and is the same for all players, but each player starts at a random position on the list.