As a reminder, and info for people who weren't playing, last summer they added new main storyline quest, the Search for Sabina parts 1-4. The new questline remains in the game forever - it won't go away, and you can do it in your own time. I still haven't finished it!
On the same day, a separate, timed goal ("event"?) was also released. If a player finished steps 1-8 and 10 of the new questline within the time limit, a special reward was received. It was the wisp "pet" which dropped stuff without having to fight fauns. It has been darn valuable.
It took heavy resources to finish the specific parts of the quest (for a broke newbie like me) within the time limit - it included expansion squares which wiped out my budget, lol. But after that time period expired, there was no way to get that reward. (A similar pet was later offered in the Market for gems.)