PRO TIP: Do the Arena teaser before Legacy drops since the badge will upgrade
The arena teaser gives out a badge. That badge apparently will turn into a cooler version of the "Arena winstreak" badge next week.
If you did not do the teaser, you will still get an "Arena winstreak" badge, but it will be a less cooler one.
(source)
So, make sure that you take some time and walk through the teaser!
Here is a video that shows what to do.
