The Granolith is a major macguffin and gimmick in Season two of Roswell. It’s discovered by Isabel at the end of the episode “Surprise”, in an underground chamber connected to the Pod Chamber. It looks like a black cylinder, at least three meters tall and about half as wide, balanced with the point down.
The Granolith was an item of immense significance back on the alien homeworld, Antar, and other worlds also, but we never get many answers about what it is or who made it. There are indications that it’s venerated in the same way as a religious relic, (comparable to the Holy Grail,) but the only powers we know it has are functioning as a starship and opening a rift to let somebody go back in time.
Alien enemies frequently try to find the Granolith, starting with congresswoman Vanessa Whittaker, and including her “brother” Nicholas and the rest of the Copper Summit skins. At the end of the season, though he’s refused to surrender the granolith to anybody else no matter what, Max allows Tess to use it to return home.