https://www.elderscrollsonline.com/en-us/news/post/62997
You can access a bunch of paid expansion content free, although the usual benefit is having all the inventory clutter (potion ingredients, crafting material, etc.) put in an infinite-use "craft bag". So, if you already have characters, log into all those and their rocks/pebbles/plants/etc. will be stored safely for future use.
The trial overlaps with the Explorer "event" which gives double XP, harvesting node rewards, etc. If you buy the High Isle expansion (the newest one, which isn't included in the trial), you can also claim the upcoming Firesong DLC free. Dunno if it's any good -- Deadlands was pretty mediocre last year, if you ask me -- but whatever.
https://gamefaqs.gamespot.com/a/user_image/0/8/9/AABhrNAADTNB.jpg
Take me down from the ridge where the summer ends
And watch the city spread out just like a jet's flame