A series of retro-clone or retro-inspired games derived from older versions of D&D.
The designer has described it as:
"Dark Dungeons is around 90% BECMI/RC emulation and 10% my house rules.
"Darker Dungeons is around 70% BECMI/RC emulation and 30% my house rules.
"Darkest Dungeons was going to be around 50% BECMI/RC emulation, 20% Rolemaster 2e emulation and 30% my house rules.
"Darkest Dungeons is now around 10% BECMI/RC emulation, 70% Rolemaster 2e emulation, 10% 3.5 SRD emulation, and 10% my house rules."