What is GANTZ the black ball? Explained

Gantz the black ball is a ball man made by an advaned organization or goverment manfactured in a foregin country (not explained which) but most likely germany because they showed a big gantz ball being worshipped there and the ball is deployed in city apartment rooms or abandoned random school classrooms around the world the combat aliens that already reside on earth that can only been seen by Gantz members and not the masses but a certain climax reaches in the series where civilization are able to see the aliens as well. Gantz is also human powered which lives off the balls energy. If the man inside the Gantz ball die, the team itself distinergrates becauses Gantz is what keeps them alive during their second life. Its also said that gantz was created to prep for a nuclear war. Theres also thousands and thousands of gantz balls being created as shown in chapter 285 in the manga.

Also again yes, there are multiple gantz teams around the world that are shown towards the final arc/ending of the manga.