Those weirdos went to Antarctica to perform some satanic ritual while viewing the total eclipse. Tartarus is Greek for the abode where the Titans were imprisoned. Also some versions of NT say certain fallen angels were chained in darkness there, awaiting judgment. Most Bibles translate it as hell.

2 peter 2:4 Berean Literal Bible For if God did not spare the angels having sinned, but having cast them down to Tartarus, in chains of gloomy darkness, delivered them, being kept for judgment;

Maybe they went there to attempt to open a portal for their "gods."