Worlds Mystery Items
Mystery items are self mystery gifts that are available from October 4 - October 23 at 23:59 PT. You can only buy 20 mystery items every 24 hours (if you buy an item at 2:00 PM on October 4, you can only buy 20 items until 2:00 PM on October 5).
Mystery Champion: 490 RP
Mystery champions may contain any champion you don't own that is worth at least 585 RP.
Mystery Skin: 490 RP
Any 520 RP or higher skin for a champion you own is eligible for mystery gifting. This includes Legendary and Ultimate skins! Legacy skins are also available, with the exception of Achievement skins, Collector's Edition skins, PAX skins, Rusty Blitzcrank, Urf the Manatee, Championship Riven, and Riot Squad Singed. Mythic skins (crafted from gemstones) cannot be mystery gifted.
Mystery Chest: 790 RP
Mystery Chests are upgraded versions of Mystery Skins - it guarantees that the skin will be worth at least 975 RP.