While most of SL content distributing through public channels, some part remains private. Many of SL episodes have more story to tell and more graphic to show (be warned that some of that content are explicit). 

IMPORTANT: People under the age of eighteen aren't allowed to be on the private channel.
IMPORTANT: Existing members are strictly prohibited from inviting underage to join. If the administration finds out that someone invites underage, he (or she) will be globally blocked!

Superhero Landing: Private is a group of channels, every channel designed for specific type of content, to get the most of it, we recommend you to find a way and join all of these channels: 

Facebook Closed Group

Instagram Private

Telegram Private (read instructions carefully)

A person has to be invited to join these channels. Usually, people get an invitation from their friends or invited directly by the channel administration. 

Multiple Reddit and Quora users say that every person gets only one or two invite-code, and some of them reported that all SL campaign backers eligible to join SL: Private on their request.