Teamfight Tactics has just been updated to 12.18, including new events, buffs, and an item nerf.
Riot Games claims that the patch includes "a great deal of enhancements to underperforming comps, including a few Dragons". Last week, the developer also revealed that "We also shipped a number of balance changes last week, during a mid-week update you can catch up on here. However, in addition to all that, the Secrets of the Shallows event begins, allowing you to join Pengu and Co on an adventure to the Uncharted Realms."
The Last Whsiper item has had its Armour Penetration reduced from 60% to 50%, along with Eternal Whisper (Radiant) getting the same reduction.
On the Riot Games game updates page, you can find all of the (extreme) Teamfight Tactics update notes, including all of the buffs and nerfs.