Teamfight Tactics has just been updated to version 12.18, adding a new events, buffs/nerfs to units, and even an item nerf.
Riot Games has said that patch is “full of buffs to underperforming comps, with a focus on reroll comps and a few Dragons”. The developer also added that “We also shipped a number of balance changes last week during a mid-week update you can catch up on here. But in addition to all that, the Secrets of the Shallows event begins, allowing you to join Pengu and Co on an adventure to chart the Uncharted Realms”.
Starting this patch, you’re invited to join Pengu and Co on an adventure to chart the Uncharted Realms with the Secrets of the Shallows event! You’ll have until patch 12.20 to explore the lands of our new Origins (Lagoon, Darkflight, and Nomsy’s home) and earn free content.
There’s a massive amount of nerfs and buffs, included the Last Whsiper item, which has had the Armour Penetration reduced from 60% to 50%, along with Eternal Whisper (Radiant) getting the same reduction.
You can grab all the (extensive) Teamfight Tactics update notes including all the buffs and nerfs on the Riot Games game updates page.