competitive tickets

The tickets will allow you to participate in the competitive tournamet. With that said the tickets you have bought will be found in the loot and after you open it they'll be used in the competitive tournament. [zombie-brand-clap]

https://nexus.leagueoflegends.com/en-us/2017/12/riot-pls-2017-and-beyond/

Whole vid is good but skip to halfway for the answer.

Also a blog: https://nexus.leagueoflegends.com/en-us/2017/12/dev-clash/

I was also curios, so I bought one. Nothing happened. WTF? Then I went to purchased items and found that it is not refundable. So I got like 39 days of First win of the day reward wasted. Am I stupid or something?

they are displayed in the loot section

I guess I am not seeing what you do. The only time I ever saw Box of Tickets was when I bought it and now in my Purchase History as Not Refundable. When I bought it there was "Get everything you need to start Hextech Crafting" and not a word about Competitive Tournament. So I bought it out of curiosity as something maybe useful for Hex. Never appeared in my Loot. And I cannot donate it to a friend or anything... But charging my BE balance works perfectly.