An RTA run where the player must complete a Spelunky Classic Low% City of Gold run, a Spelunky HD Chain Low% Hell run, and either a Spelunky 2 Chain Low% Abzu or Chain Low% Duat run in order. In the Spelunky HD Chain Low% Hell run, the Udjat Eye is optionally allowed to be collected. Only Spelunky Guy or Damsel are allowed in Spelunky Classic.
Timing instructions can be found here