Riot Games has designed a new Teamfight Tactics mechanic for Set 12 called Charms, which grants you power level effects in each Stage of a Magic n' Mayhem match.
Quick Guide for Charms || TFT SET 12
Riot created the new TFT Set 12 mechanic Charms to reduce the randomness seen in previous mechanics. This comes after heavy player criticism of Set 11’s Encounters. Instead of random effects on Carousels, or more Armories alongside Augments, the Charm mechanic will appear in a player’s store. The design is a vast improvement over Encounters, in my opinion after testing it out previously.
The flavor of Charms is spot-on for a set called Magic n' Mayhem, as these new Charms grant you different effects in each Stage. Over 100 Charms are included in TFT Set 12, which has its pros and cons.
For new and casual players, it’s hard enough to memorize Augments that synergize with comps, new traits, and 50+ champion abilities, let alone 100+ Charms. But don’t let the stats overwhelm you, as most Charms contain temporary effects that last for one round of combat.