[Ray88]

"TLDR:
New tier placed between Diamond 1 and Challenger.
You access to Master Tier once you've been successful in your D1 promo
Once you are in Master Tier you can compete to reach Challenger Tier. There is no player limit in Master Tier.
Challenger players will now rotate every 24h, taking all the top 200 players in Master Tier and promoting them to Challenger, switching places with people in Challenger below top 200.
No more immunity for newest challenger players"

it's nice but rito should add tiers lower then bronze kappa

source: reddit