@dotcomrobots Both Neverwinter and Elder Scrolls Online are taken down regularly for updates. As far as what they are addressing during these maintenance windows varies quite a bit. They can be down for several hours as a result.
For example, here is a recent post from ESO concerning planned downtime:
Hi everyone!
Over the next couple weeks, we’ll be performing updates to the databases associated with various services (things outside of the game such as the login system). We’re planning to focus on one platform per maintenance window, which will include NA & EU, and will have staggered openings where needed. All timings are outlined below:
Wednesday, April 24:
PC/Mac and PS4: 4am to 8am EDT
XB1: 4am to 12pm EDT
Tuesday, May 7:
XB1: 4am to 8am EDT
PS4: 4am to 12pm EDT
Monday, May 13:
PC/Mac: 4am to 12pm EDT
Edit: The PC/Mac maintenance previously scheduled on May 6 moved to May 13.
Edit 2: The console maintenance previously scheduled on May 8 moved to May 7.