Thanks, makes a little more sense now....except what the fuck does "S" stand for?a few things. one is champion mastery. which was previously only Summoners rift.
Champion Mastery - League of Legends Wiki - Wikia
Tier 1
badge
Tier 2
bigger badge
Tier 3
biggerer badge
Tier 4 - biggererer Loading Screen Badge, Custom Emote, Announcement Banner
Champion mastery tier 5
Tier 5 - biggerererer Loading Screen Badge, Custom Emote, Announcement Banner
and Titles
Champion Mastery - League of Legends Wiki - Wikia
Mastery then is related to hextech crafting.
you get a chest when you or someone in your premade team gets an S rank. 4 chests total per rank, only 1 per champion played.
Keys and key fragments for the chest, any time you win.
I also didn't see anything on the wiki about the custom announcement.