Mystery Skin vs Mystery Chest?

Solution 1:

From the Riot Games Mystery Gifting FAQ:

Is it possible for my friend to receive a skin for a champion they don't own?

Nope, your friend can only receive skins for Champions they already own. For example, your friend cannot receive Jade Dragon Wukong if they don't already own Wukong as a Champion.

What about skins my friend already owns?

Your friend can only receive a skin that they don't already own. No duplicate skins will be added to their account.

From the Riot Games Mystery Chest FAQ:

What is a Mystery Chest?

Mystery Chests are upgraded versions of Mystery Gifts. For 790 RP, you can send a random mystery skin to your friend that is worth 975 RP or more.

What skins are eligible for Mystery Chest?

Any skin that meets all of the following requirements is eligible:

• Your friend owns the champion for the skin
• The skin is worth at least 975 RP
• The skin is available for purchase in the store*

*Legacy skins will also be obtainable as a Mystery Skin EXCEPT Achievement skins, Collector's Edition skins, PAX skins, Rusty Blitzcrank, Urf the Manatee, Championship Riven and Riot Squad Singed. Mythic skins that can be crafted with gemstones will not come from Mystery Chest.

Note: it is NOT possible to gift your friend a skin that he/she already owns.