TGOD, short for The Good Old Days, was recurring thread that originated in about 1999 on the newsgroup alt.startrek.vs.starwars. In a TGOD thread, the goal was to "kill" people (usually another ASVS denizen) in amusingly creative ways. Other than that, there were no real written rules: it was assumed to all be in good fun, and laughs could be had all around. A complete index of the old ASVS TGODs and STGODs can be found on the ASVS Fanfic Archive.
They grew rather rapidly in popularity in the newsgroup and as they did, arguments began to spring up over how someone's character was killed and/or resurrected. Due to this, in the winter of 1999 the first STGOD was created with about a dozen participants. STGOD stands for Structured TGOD, and essentially the only addition was that of Phong Nguyen as the moderator, who with his Mallet of Doom (tm) would stop such silly arguments from happening.
Over time, the STGODs grew in size and length. Most of the participants had ridiculously overpowered nations toward the end: every nation had more than one weapon capable of killing planets, and quite a few nations had weapons capable of killing stars. One nation, in fact, wound up "consuming" about 1,000 galaxies--by accident! Eventually a reboot of the universe was forced, downscaling the STGODs, and in the process interest dropped.
In 2004, after the Stardestroyer.net BBS was created, a number of ASVS denizens attempted to bring the STGOD with them onto the group. Transitioning from a threaded format (where replies were sorted in trees and could be easily navigated through) to a linear format, with replies sorted by date, was a major setback. In addition, much of the culture that had created the STGODs was lost as modern Web boards generally have a much different user base than Usenet did in 1999.
As a result, interest in the STGODs in their original form was lost, replaced by a more board-style strategy game with a general set of rules. Pre-game rule discussions and out of character disputes generally take up far more time and posts than the actual games themselves.
To most people now on SD.net, STGOD stands for Science Fiction TGOD, and FTGOD stands for Fantasy TGOD.
The most notable article here is the Unofficial TGOD Handbook, a work in progress meant to contain all the basic information a TGOD needs to run. Eventually that article will be completed, become an Official TGOD Handbook and be put here instead as a resource for all other TGOD games.