Concept art for six heroes that haven’t been released yet have surfaced on Reddit.
According to user PurgeGamers, the photos were taken at Valve last thursday. The heroes featured are all derived from the classic DotA mod for Warcraft III.
Purge Gamers added in one of his comments that, while he was there, he was able to play Skywrath as well as Bristlebog (not shown below).
Abyssal Underlord (Pit Lord)
Chieftain/Elder Titan (Tauren Chieftain)