The game was abandoned and official servers went down in 2018.
Tribes: Ascend is the newest iteration in the franchise that begun in 1998 with Starsiege Tribes. After Hi-Rez Studios aquired the franchise, they first intended to create a MMOFPS called Tribes Universe. Soon they changed their focus towards a more traditional multiplayer FPS and changed the name to Ascend.
Tribes: Ascend focusses on movement. Each player has a jetpack and the ability to eliminate friction to glide downhill, called skiing.
Source: The Game Website.