You can run it pretty swell with D9VK, to do so just download Lutris and then search for Tera, then just google how to swap the runner from whatever the packaged installer uses to D9VK (https://github.com/Joshua-Ashton/d9vk) and you'll be good to go, from my experience testing it on different games as well as Tera the performance is on-par for the most part, however it might be unstable due to the list of default d3d9.dlls that comes with the installer so you might have to play around with it until you reach PC-like stability (D9VK comes with their own D3D9.dlls so read up on the github repo which ones you should remove from the wine config on lutris.
EDIT: The game was tested on Arch Linux so your mileage may vary.
