The Elder Scrolls: Legends’ Chaos Arena first debuted in December and came back for a limited-time engagement in January. The mode has apparently proven popular enough for Bethesda to add it to the game as a semi-regular feature.
The game mode runs this weekend, from Feb. 17-20, and will return for one weekend every month. If you need a refresher on how the mode works, you can check out the description on the TES: Legends site. The tl;dr version: It’s like regular Arena but with more, well, chaos. What else would you expect from Sheogorath?