Custom skins are skins for League of Legends that only the user of the skin can see. Skins on oberonkingdom.com are created under Riot Games’ “Legal Jibber Jabber” policy using assets owned by Riot Games. Riot Games does not endorse or sponsor this project.
There are currently 2 safe methods to install custom skins. These are Fantome and LCS Manager. To learn about how to install and use custom skins with these apps, check out the installation guides.
Custom Skins that are installed by using Fantome or LCS Manager are safe to use which won’t get your account banned (as long as you don’t use it to install an official skin created by Riot Games for free).
There are many famous content creators (Cowsep, RossBoomSocks, iPav999 for example) that use Custom Skins very publicly for many years now and they haven’t been banned for using these apps. This should give you some reassurance that you won’t get banned for using them as long as they don’t.