TERA is Headed to the En Masse Launcher Starting Today
For a number of technical reasons, TERA will be moving to the En Masse Launcher starting today. The goal is to provide an improved experience to the entire En Masse player community as well as to the specific TERA community. "The En Masse Launcher, and other upcoming changes, are part of a company-wide effort aimed at changing the philosophy" that benefits individual games, but provided "less value" to the player community as a whole.
Most notably, all of EME's games will be hosted on the En Masse Launcher in a "shared ecosystem" that allows devs to improve the player experience through simplified patching, a cleaner interface, better access to social channels, fewer restarts, and more streamlined communication.
You can read the full notice on the TERA site.