Half-Life : 25th Anniversary Challenges mod
This mod has been built for experienced HL gamers who want to experience a more challenging HL experience. This mod includes 2 different storylines, including a new one with levels based on OP4, Decay, Training, and Black Mesa. It also includes 5 different...
Unforeseen Consequences Late Mapping Half Life 25th Anniversary Challenges Mod Half Life Otal Conversion Xpansion Pack
Source: moddb.com