If you’re trying to play Elder Scrolls Online on macOS Sierra or higher, you may encounter the application crashing on launch, especially on new installs. Specifically, this is likely to occur right after clicking Play in the launcher. The specific error message is:
Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000078 Exception Note: EXC_CORPSE_NOTIFY Termination Signal: Segmentation fault: 11 Termination Reason: Namespace SIGNAL, Code 0xb Terminating Process: exc handler 
This appears to be caused by an issue with how the game handles the number of cores on your machine. I found the following fix on the Elder Scrolls Online forums, but it wasn’t well-documented, so it took me a bit of stumbling around to actually get things working.
This is a two-part fix. The first part involves changing the number of cores that ESO is allowed to use so that it will run once, and then adjusting it’s configuration file to fix it for every launch.
Some users have reported success with only creating a changing the UserSettings.txt file. When I tried this, it resulted in game freezes and instability. Your mileage may vary, but going through all of the steps below worked for me with a minimum of hassle and kept the game stable throughout.
First launch fix – Limit the number of cores
To do this, first go to the App Store and install Xcode.
Once Xcode is installed on your system, run Instruments.
Once Instruments starts, go to Instruments > Preferences and limit the number of Active processor cores to half of whatever your maximum number is:
After you make this change, start the game normally, log in to the game until you’re able to move your character around, then log out. Exit the game completely and change the number of cores back to the maximum in Instruments. then move on to the next section to find out how to make a change in the game’s config files to eliminate the need to use Instruments for subsequent game starts.
Subsequent Launch Fix – Edit the UserSettings.txt file
Open the UserSettings.txt file with TextEdit. The file is usually located at:
Documents/Elder Scrolls Online/live/UserSettings.txt
Find the following lines:
SET RequestedNumJobThreads "-1" SET RequestedNumWorkerThreads "-1"
Change them to:
SET RequestedNumJobThreads "0" SET RequestedNumWorkerThreads "0"
Save the document, and start Elder Scrolls Online once again.