Core Adventures are RPGA Living Greyhawk scenarios that take place in the nonregional areas of the game world: the City of Greyhawk, the Nyr Dyv, the Duchy of Tenh, the Underdark, etc. Cores can be played by any PC, anywhere in the world. Cores advance campaign-wide plots.
The Core series of scenarios were provided for RPGA Network play (a precursor to Organized Play), and were distributed electronically on a limited basis to participating Dungeon Masters. While the scenarios are linked by geography and theme, they were not intended as a continuous "adventure path".
Because players used their own characters in Living Greyhawk, each of the scenarios supported a fairly wide range of character levels; this was accomplished by noting various adjustments the Dungeon Master could use "on the fly" to set the adventure at an appropriate difficulty depending on the actual characters engaged for the session.
Core Season Four, played throughout 2004, took place in Common Year (CY) 594.